Typescript

I don't use it personally, and I find that it visually messes with me in code I am working on (I am dyslexic and inline types make js unreadable to me) so I'd rather someone that uses it PRs for non-invasive type stuff.

The tooling (tests/build/ui) is all setup in vite/microbundle, which should be pretty drop-in (add tsconfig and some types in a separate file.)