Used a copy of .gitignore of mediawiki/core and removed some lines, because in this extension not all the folders which are in core. Change-Id: I17a0a2802d1ed8b58c1096142024ec1ef12680e2
This is the final step of the process described at <https://www.mediawiki.org/wiki/Separating_skins_from_core_MediaWiki>. Corresponding core change: Idfc38503. Change-Id: I83b1efb4a489254c76e0cbda72ff34efa3d41261