[DOCS] Add note about limitations of CKEditor5 CSS styling

Resolves: #103310
Resolves: https://github.com/TYPO3-Documentation/Changelog-To-Doc/issues/859
Related: #103151
Related: #100768
Releases: main, 12.4
Change-Id: Ia1769439da1b85fc437ec3aca80f722b981eb183
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83238


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>