[DOCS] Overview of form elements

This patch adds a documentation regarding form
elements for editors.

As a drive-by change the site trees for integrators
and editors have been fixed.

Resolves: #82357
Releases: main, 11.5
Change-Id: I06548dd0f51cdbd814067f1c44e49629fd56b68e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73700


Tested-by: core-ci <typo3@b13.com>
Tested-by: waldhacker <hello@waldhacker.dev>
Reviewed-by: waldhacker <hello@waldhacker.dev>