Adding configuration for #brickimedia

I've added mediawiki/extensions/MediaWikiChat to be fed to the #brickimedia IRC
channel. MediaWikiChat is an extension by Brickimedia so we'd like to have its
changes fed to our channel like our other repos are (however those are on GitHub).

Change-Id: I8609c619073075da49b5ababb58e6f66f32a6f6c