Go WASM UI framework

[tj]

I played with Go WASM a bit last year and didn't have much luck, but I wouldn't mind exploring it some more.

I think Rust is too overkill personally, and Elm is too restrictive (from what I tried at least), plus just using the same language on the client/server would be great, especially for making stuff like #16 really seamless.

This would be a suite of packages, but I'll create distinct issues for them later.