[cmake][doc] rename cmake option, export it to find_package(), add doc.

[poor-circle]

What is changing

1. export some option for user when they import ylt by cmake find_package()/fetchContent()
2. rename the option(add YLT_ prefix) to avoid name conflict.

Example

[github-actions]

Code Coverage Report
for detail, goto summary download Artifacts

Filename                                       Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
coro_io/channel.hpp                                   14                 0   100.00%         105                 3    97.14%          30                 2    93.33%
coro_io/client_pool.hpp                               29                 1    96.55%         358                69    80.73%         140                51    63.57%
coro_io/coro_file.hpp                                 22                 2    90.91%         213                46    78.40%          56                21    62.50%
coro_io/coro_io.hpp                                   37                 1    97.30%         212                 9    95.75%           4                 0   100.00%
coro_io/detail/client_queue.hpp                       10                 1    90.00%          47                 1    97.87%          10                 1    90.00%
coro_io/io_context_pool.hpp                           34                 3    91.18%         198                13    93.43%          24                 5    79.17%
coro_io/rate_limiter.hpp                              11                 0   100.00%          83                 8    90.36%           8                 3    62.50%
coro_rpc/impl/common_service.hpp                       1                 0   100.00%           8                 0   100.00%           4                 0   100.00%
coro_rpc/impl/coro_connection.hpp                     25                 7    72.00%         267               149    44.19%          80                57    28.75%
coro_rpc/impl/coro_rpc_client.hpp                     20                 5    75.00%         166                18    89.16%          44                12    72.73%
coro_rpc/impl/coro_rpc_server.hpp                     12                 0   100.00%         174                16    90.80%          62                27    56.45%
coro_rpc/impl/errno.h                                 10                 3    70.00%          43                31    27.91%          26                13    50.00%
coro_rpc/impl/protocol/coro_rpc_protocol.hpp           6                 1    83.33%          83                26    68.67%          24                 9    62.50%
coro_rpc/impl/router.hpp                               5                 0   100.00%          93                17    81.72%          30                13    56.67%
easylog.hpp                                            8                 0   100.00%          41                 3    92.68%          12                 4    66.67%
easylog/appender.hpp                                  22                 0   100.00%         266                18    93.23%          88                26    70.45%
easylog/record.hpp                                    17                 0   100.00%         111                 4    96.40%          16                 2    87.50%
struct_pack.hpp                                        3                 2    33.33%          29                 7    75.86%           0                 0         -
struct_pack/calculate_size.hpp                         7                 0   100.00%         215                17    92.09%           6                 5    16.67%
struct_pack/derived_helper.hpp                         2                 2     0.00%           6                 6     0.00%           0                 0         -
struct_pack/endian_wrapper.hpp                         6                 3    50.00%          86                28    67.44%           2                 1    50.00%
struct_pack/error_code.hpp                             6                 6     0.00%          30                30     0.00%           0                 0         -
struct_pack/foreach_macro.h                            1                 1     0.00%           1                 1     0.00%           0                 0         -
struct_pack/md5_constexpr.hpp                          7                 7     0.00%          31                31     0.00%           0                 0         -
struct_pack/packer.hpp                                 9                 2    77.78%         385                27    92.99%          18                13    27.78%
struct_pack/reflection.hpp                             9                 6    33.33%         628                81    87.10%           0                 0         -
struct_pack/size_info.hpp                              2                 0   100.00%          10                 0   100.00%           0                 0         -
struct_pack/tuple.hpp                                  1                 1     0.00%           1                 1     0.00%           0                 0         -
struct_pack/type_calculate.hpp                        21                21     0.00%         479               479     0.00%           0                 0         -
struct_pack/type_id.hpp                                2                 2     0.00%         198               198     0.00%           0                 0         -
struct_pack/util.h                                     5                 3    40.00%          35                14    60.00%           4                 0   100.00%
struct_pack/varint.hpp                                 1                 1     0.00%           3                 3     0.00%           0                 0         -
util/concurrentqueue.h                                79                19    75.95%        1252               562    55.11%         292               157    46.23%
util/dragonbox.h                                      90                50    44.44%         735               388    47.21%          38                34    10.53%
util/dragonbox_to_chars.h                              6                 2    66.67%         440               381    13.41%          54                46    14.81%
util/expected.hpp                                     17                 3    82.35%          21                 3    85.71%           2                 0   100.00%
util/meta_string.hpp                                  10                 3    70.00%          46                23    50.00%           8                 0   100.00%
util/time_util.h                                      13                13     0.00%         156               156     0.00%           0                 0         -

Files which contain no functions:
struct_pack/marco.h                                    0                 0         -           0                 0         -           0                 0         -
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                580               171    70.52%        7255              2867    60.48%        1082               502    53.60%

[github-actions]

Code Coverage Report
for detail, goto summary download Artifacts

Filename                                       Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
coro_io/channel.hpp                                   14                 0   100.00%         105                 3    97.14%          30                 2    93.33%
coro_io/client_pool.hpp                               29                 1    96.55%         358                57    84.08%         140                44    68.57%
coro_io/coro_file.hpp                                 22                 2    90.91%         213                46    78.40%          56                21    62.50%
coro_io/coro_io.hpp                                   37                 1    97.30%         212                 9    95.75%           4                 0   100.00%
coro_io/detail/client_queue.hpp                       10                 1    90.00%          47                 1    97.87%          10                 1    90.00%
coro_io/io_context_pool.hpp                           34                 3    91.18%         198                13    93.43%          24                 5    79.17%
coro_io/rate_limiter.hpp                              11                 0   100.00%          83                 8    90.36%           8                 3    62.50%
coro_rpc/impl/common_service.hpp                       1                 0   100.00%           8                 0   100.00%           4                 0   100.00%
coro_rpc/impl/coro_connection.hpp                     25                 7    72.00%         267               149    44.19%          80                56    30.00%
coro_rpc/impl/coro_rpc_client.hpp                     20                 5    75.00%         166                18    89.16%          44                12    72.73%
coro_rpc/impl/coro_rpc_server.hpp                     12                 0   100.00%         174                16    90.80%          62                27    56.45%
coro_rpc/impl/errno.h                                 10                 3    70.00%          43                31    27.91%          26                13    50.00%
coro_rpc/impl/protocol/coro_rpc_protocol.hpp           6                 1    83.33%          83                26    68.67%          24                 9    62.50%
coro_rpc/impl/router.hpp                               5                 0   100.00%          93                17    81.72%          30                13    56.67%
easylog.hpp                                            8                 0   100.00%          41                 3    92.68%          12                 4    66.67%
easylog/appender.hpp                                  22                 0   100.00%         266                18    93.23%          88                26    70.45%
easylog/record.hpp                                    17                 0   100.00%         111                 4    96.40%          16                 2    87.50%
struct_pack.hpp                                        3                 2    33.33%          29                 7    75.86%           0                 0         -
struct_pack/calculate_size.hpp                         7                 0   100.00%         215                17    92.09%           6                 5    16.67%
struct_pack/derived_helper.hpp                         2                 2     0.00%           6                 6     0.00%           0                 0         -
struct_pack/endian_wrapper.hpp                         6                 3    50.00%          86                28    67.44%           2                 1    50.00%
struct_pack/error_code.hpp                             6                 6     0.00%          30                30     0.00%           0                 0         -
struct_pack/foreach_macro.h                            1                 1     0.00%           1                 1     0.00%           0                 0         -
struct_pack/md5_constexpr.hpp                          7                 7     0.00%          31                31     0.00%           0                 0         -
struct_pack/packer.hpp                                 9                 2    77.78%         385                27    92.99%          18                13    27.78%
struct_pack/reflection.hpp                             9                 6    33.33%         628                81    87.10%           0                 0         -
struct_pack/size_info.hpp                              2                 0   100.00%          10                 0   100.00%           0                 0         -
struct_pack/tuple.hpp                                  1                 1     0.00%           1                 1     0.00%           0                 0         -
struct_pack/type_calculate.hpp                        21                21     0.00%         479               479     0.00%           0                 0         -
struct_pack/type_id.hpp                                2                 2     0.00%         198               198     0.00%           0                 0         -
struct_pack/util.h                                     5                 3    40.00%          35                14    60.00%           4                 0   100.00%
struct_pack/varint.hpp                                 1                 1     0.00%           3                 3     0.00%           0                 0         -
util/concurrentqueue.h                                79                19    75.95%        1252               564    54.95%         292               159    45.55%
util/dragonbox.h                                      90                50    44.44%         735               388    47.21%          38                34    10.53%
util/dragonbox_to_chars.h                              6                 2    66.67%         440               381    13.41%          54                46    14.81%
util/expected.hpp                                     17                 3    82.35%          21                 3    85.71%           2                 0   100.00%
util/meta_string.hpp                                  10                 3    70.00%          46                23    50.00%           8                 0   100.00%
util/time_util.h                                      13                13     0.00%         156               156     0.00%           0                 0         -

Files which contain no functions:
struct_pack/marco.h                                    0                 0         -           0                 0         -           0                 0         -
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                580               171    70.52%        7255              2857    60.62%        1082               496    54.16%