MediaWiki theme: Fix ButtonWidget (frameless, indicator) `:focus` appearance
MediaWiki theme: Fix ButtonWidget (frameless, indicator) `:focus` appearance

Make `:focus` state of frameless ButtonWidget with indicator appear padded
on both sides.

Bug: T141249
Change-Id: I5ecc7c58b13a1cd0a50a5bd804bb3646cf81b20e

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui