[TASK] Update "workspaces" documentation

Update documentation of extension "workspaces".
Move all TSconfig related options here (over from TSconfig reference).
Update rendering configuration (for docs.typo3.org).

Resolves: #76799
Releases: 7.6, master
Change-Id: Ife7e4536fba82dcdd2a5eb8c1ae9a4fecc0d3fae
Reviewed-on: https://review.typo3.org/48696


Reviewed-by: Francois Suter <francois@typo3.org>
Tested-by: Francois Suter <francois@typo3.org>