[TASK][DOC] New chapter "Frequently Asked Questions"

Change-Id: I19ddb57a22ba9d2d29673304dd1bb60567be6ee1
Reviewed-on: https://review.typo3.org/31628
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>