Recommendation is to avoid using the year nomenclature as this
information is already encoded in the git repo. Avoids needing to
repeatly update.
Also updates AUTHORS.txt from current repo with contributor names
Currently, unselecting the bold option resets the thickness to the
standard size instead of reverting to the original thickness.
To address this, the original thickness should be preserved so it
can be restored when bold is turned off.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/18975
* Add compare method to COLOR4D object.
* Add unit test to validate COLOR4D comparison method.
* Add missing color test in text attribute comparison method.
* Add unit test for text attribute object.
* Remove unnecessary headers from text attribute header.
* Move text attribute code into separate source file.
