[TASK] Writing documentation

Merges forgotten commit from the past and fix some missing files during merge process. Sorry, this is my first try.

Relates: #58535
Change-Id: I8ce02b05e193a45a62cb2c4c653fef60bd4b72e6
Reviewed-on: https://review.typo3.org/31078
Reviewed-by: Armin Ruediger Vieweg
Tested-by: Armin Ruediger Vieweg