Add TypeScript

[bvisness]

Now that TypeScript is written in Go, we can actually add it to our workflow very easily. Support has been added to our Esbuild config just like for CSS, and TS can be run like go tool tsgo -p src/rawdata/js.

The structure of src/rawdata/js is: all files directly in that folder are considered an entry point, while all files in /lib are not and must be imported via ESM imports. The general expected pattern is one JS file per page that imports whatever it needs.

This implies that we should move away from plain old scripts on the page, onclick="foo" attributes, etc. etc.