Activate the "other projects" sidebar managed by Wikibase in itwikisource

Enabling itwiki, itwikiquote, itwikivoyage and commonswiki as other projects.

bug: 63993
Change-Id: Idbc0d0bc616e83fe768996cbec168216517a96f9
Merge "Activate the "other projects" sidebar managed by Wikibase in itwikisource"