Topic escape characters (ros2#3802)

* doc fix for rcutils environmental variables.

* RCUTILS_CONSOLE_OUTPUT_FORMAT escape sequences support table.

Signed-off-by: Tomoya.Fujita <Tomoya.Fujita@sony.com>

source/Tutorials/Demos/Logging-and-logger-configuration.rst

@@ -377,7 +377,7 @@ Restart the demo including the following command line arguments:
 Console output formatting
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-If you would like more or less verbose formatting, you can use RCUTILS_CONSOLE_OUTPUT_FORMAT environment variable.
+If you would like more or less verbose formatting, you can use the ``RCUTILS_CONSOLE_OUTPUT_FORMAT`` environment variable.
 For example, to additionally get the timestamp and location of the log calls, stop the demo and restart it with the environment variable set:
 
 .. tabs::
@@ -406,6 +406,24 @@ For example, to additionally get the timestamp and location of the log calls, st
 You should see the timestamp in seconds and the function name, filename and line number additionally printed with each message.
 *The ``time`` option is only supported as of the ROS 2 Bouncy release.*
 
+``RCUTILS_CONSOLE_OUTPUT_FORMAT`` also supports the following escape character syntax.
+
+.. list-table::
+    :header-rows: 1
+
+    * - Escape character syntax
+      - Character represented
+    * - ``\a``
+      - Alert
+    * - ``\b``
+      - Backspace
+    * - ``\n``
+      - New line
+    * - ``\r``
+      - Carriage return
+    * - ``\t``
+      - Horizontal tab
+
 Console output colorizing
 ^^^^^^^^^^^^^^^^^^^^^^^^^