implement spell-checking in Dockerfile.test

[modernNeo]

https://github.com/pylint-dev/pylint
https://pylint.readthedocs.io/en/latest/user_guide/configuration/all-options.html#spelling-checker
https://pyenchant.github.io/pyenchant/install.html

currently blocked by:

To detect the libenchant binaries, PyEnchant uses [ctypes.util.find_library()]  
(https://docs.python.org/3/library/ctypes.html#finding-shared-libraries), which requires ldconfig, gcc, objdump or ld to be installed.  
This is the case on most major distributions, however statically  
linked distributions (like Alpine Linux) might not bring along binutils by default.

pyenchant/pyenchant#164
docker-library/python#111
python/cpython#65821
python/cpython#18380