- Added the file to `riot.doxyfile`
- Shortened the header to display properly
- Added `[TOC]` to let doxygen create a table of contents
- Added manual anchors to the headers for consistency with other doc files
- Use @code and @endcode for code blocks (using fenced blocks doesn't parse
with the Doxygen version used by the CI)
- Changed a numbered list containing code blocks to regular text, as the code
blocks as list items are not parsed correctly
- Enforce 80 chars per line limit
- Fixed some typos
- Removed trailing whitespace
- Added markdown syntax for code highlight in two cases
- Reduced the TODO section heading from level 1 to level 2
==> No content changes
