[DOCS] Add documentation for font plugin to CKEditor5

Resolves: #103311
Resolves: https://github.com/TYPO3-Documentation/Changelog-To-Doc/issues/858
Related: #100847
Releases: main, 12.4
Change-Id: I7de8bd33e489807a634f3efb3b1c6dfd19061cc5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83267


Reviewed-by: Garvin Hicking <gh@faktor-e.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Lina Wolf <112@linawolf.de>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Tested-by: Lina Wolf <112@linawolf.de>