Highlight the target reference when the user clicks a reference link,
and also highlight the note in the text when he clicks the backlink.
This is done using the :target selector and a light blue background-color.
The color (and the rest of the code) are from English Wikipedia, from where
it has been copied to many other wikis, so the feature itself and especially
the color seem to be agreed on.
Browsers that don't support the :target selector (notably Internet Explorer 8
and below) will just ignore the new style and fall back to current behavior.
Wikis that have added this code to their common.css can remove it, but
of course nothing will break when they keep the duplicate code.
Bug: T10303
Change-Id: I5775daf6934516ce9c98841399e5a358195c1374
Steps to test the change:
* Open a random page in browser.
* Select all or a part of the page.
* Copy the selection to clipboard.
* Open a word processor like LibreOffice Writer.
* Paste the content of the clipboard.
Change-Id: Ibae4292b5dd8cc02a769e85adfea991d8d6ceb59
Had to do that in JavaScript as doing it server-side would have
made refactoring large parts of the extension necessary.
Bug: 38141
Change-Id: I60ecd2fc0edf2aee89974d8069cc0b075cda3f93
