[TASK] Document property "elementDescription"

The property "elementDescription" has been documented for both the
backend (form editor) and the frontend of the form framework.

In addition, some minor contextual and spelling problems have been
fixed.

Resolves: #84229
Releases: master, 9.5
Change-Id: Ifc9039b3dc434a20783d8d67b5d6efcd1eed113e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60609


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>