[TASK] Merge EXT:cshmanual into EXT:documentation

To reduce the amount of system extensions the extension
cshmanual can be merged into EXT:documentation.

Resolves: #81574
Releases: master
Change-Id: I5cd728938ffd319f5c13bf0af4caeda48c08ee37
Reviewed-on: https://review.typo3.org/53180


Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>