[TASK] Migrate and update documentation

Migrate the documentation to reST and update content a bit.

Resolves: #57360
Releases: 0.6
Change-Id: I8941b0318bb17ec68e023f3b5882d8ba21451f24
Reviewed-on: https://review.typo3.org/29126
Reviewed-by: Francois Suter
Tested-by: Francois Suter