Snippets/CSS link highlight

Description
This small CSS code shows redirects and desambiguation pages with a color code.

This helps to visually troubleshoot internal links. It works while reading pages, and with any page editor, or preview mode.

Usage
It should work for all types and versions of MediaWiki.
 * You can activate it centrally for all the sister projects on m:Special:MyPage/global.css
 * Or specifically for one wiki in Special:MyPage/common.css