Use ContentGetParserOutput hook instead of ShowRawCssJs

Authored by matmarex.

Description

Use ContentGetParserOutput hook instead of ShowRawCssJs

Depends on I58679856 in core MediaWiki.

This breaks compatibility with MW < 1.24.

Bug: 64859
Change-Id: Idf4ad4397101a4d19be2ac773cd4bad52188d903

Details