Background
We're currently using, browser compatibility from the old times inspired, CSS 2 notation on pseudo-elements :before and :after. Originated in MW core and OOUI.
Goal
Given our modern support baseline, let's change to ::before and ::after in our codebase, similar to already implemented ::placeholder. Read further on vast browser support (Firefox 1.5, Chrome 3, Edge, …)
Done criteria
- Replace all occurrences with CSS 3 double colon :: notation