Improve wikibase interlanguage link styles

Overrides the wikibase.client.init module to
better style the interlanguage link button in
Vector 2022.

Also adds the .mw-list-item class to that link
so that it maintains consistency with the other
menu list items.

Bug: T328069
Change-Id: I5c84b7f036afb4b8dc11e92a59dff8000f068e67