Documentation site

[dhess]

We need a documentation site:

1. We will link to it from the app.
2. We’ll probably want to embed it in the app, preferably via some sort of reusable component.
3. We’ll probably want to embed Primer programs in the docs site; e.g., for example programs.

In other words, the documentation site will be a full-blown React-based SPA of its own, though preferably most of the content will be statically rendered.

Astro looks interesting for this purpose. It’s framework-agnostic, as far as I’m aware. I believe that Docusaurus uses React under the hood, but my impression is that it’s too static for our needs. VitePress looks nice, but it uses Vue.