Proper documentation

[saiichihashimoto]

While I've put some effort into the _README.md/README.md, it's not the best. Ideally, we'd be on some hosted auto-generated site that looks nice, similar to zod.dev or other documentation sites.

Nice to haves:

• Write documentation once, get npm, github READMEs, and hosted documentation.
• For npm, should have the documentation per package.
• For github, should have the documentation per package in README.
• For the site, not entirely sure but it should certainly address all the packages.
• Some kind of templating, since we'll want to repeat some content between the packages.
• Auto deployment, I'm sure we can handle this with semantic-release.
• I bought sanity-typed.dev, have it hosted there

I don't know how these sites tend to do it and I'd love the experience of someone who's done this before!