Switch to djot

[bmschmidt]

Total revamp--this will be fun! The idea is that the [https://djot.net/] AST is cleaner and more powerful than the pandoc one, and we can convert cleanly between them, so let's

1. build the components on top of djot
2. Let people write quote-unquote markdown that's actually djot so that we can do things like SSR or in-browser rendering of scrolly-telling, which is incredibly powerful (e.g. there is no need for ESRI map stories)
3. If I'm ever able to get pandoc fully compiled to wasm with the ghc wasm backend, we can do ssr and anything on any pandoc supported format
4. until then we can use a loader that uses pandoc when it's defined as a system executable to write blog posts in ms word or whatever.

Still working out some details on intersection observer, but this:

• Satisfies full typescript compliance
• Moves to using djot's AST instead of pandoc-markdown
• Will allow real-time rendering of fancy jgm-style markdown in browser, which has been my goal for a while.