Partially realted to #188

Hey there, folk! Should we try to compile Rust Language Server into WASM to run it in the playground to provide, at least, the intellisence and completions?

I don't really know how closely it is tied to the rust compiler itself, which cannot be, as far as I know, compiled for the web at the moment. I think we really need someone with a good pack of knowledge here 😄

Performance might be an issue, but it should be possible to, in theory, run the RLS in a separate WebWorker. Maybe even compile it to use multiple of them using Emscripten and enabling SharedArrayBuffer support?