Documentation landing page

[ptheywood]

The documentation landing page needs some content other than the TOC.

Probably just some generic about flaemgpu 2 blurb + some wordy links to the main sections (quickstart, user guide, tutorial, api docs)

The TOC could probably do with some formatting tweaks (nested list stylign) and maybe depth limiting too (or even hiding entirely relying on the global nav + wordy links)