Enable Bulletin: and Event: for Wolfplex wiki search

Summary:
Those two namespaces are content namespaces.

Reference: https://www.mediawiki.org/wiki/Manual:$wgContentNamespaces

Test Plan: Search "UBO", get Bulletin: result

Reviewers: fauve

Reviewed By: fauve

Differential Revision: https://devcentral.nasqueron.org/D3084