User blog comment:Ultimate Dark Carnage/Carnage's Guide to Templates: Navboxes/@comment-5558012-20140715014552/@comment-4522253-20140715182608

Actually, Common.js would be a good place, too. As in:

importArticles({   type: "style",    articles: [        "local:MediaWiki:Navbox.css"    ] });

That way, the CSS can be put in discrete units and minified on load.