[TASK] Add .htaccess in Resources/Private/

Releases: 2.0.0
Change-Id: I7fff934df00a715061ccba7a91b761530822a177
Reviewed-on: https://review.typo3.org/31616
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>