Improve header formatting

[fluffy-critter]

Headings/subheadings look really heckin' weird right now, and part of that is because FoF seems to expect a certain base header level (which was probably from back when it was considered standard to have h1 = site, h2 = article, and therefore article headings start at h3). The HTML5 <article> semantic does.... weird stuff to this, which I still don't actually understand particularly well, but it seems like it should at least make things somewhat better?

Or at the very least the CSS rules for h1 and h2 should probably be scoped to only apply to FoF's UI itself. (But wrapping the article content inside <article> should still help with stuff. Somehow. Again, I don't really understand how it's meant to work. Old enby yells at cloud.)