feat: introduce connector for js/wasm

[x1unix]

This PR introduces js/wasm platform support to run gnopls in browsers and Node.js.

Implementation relies on 3 WebAssembly exports and syscall/js package to receive JSON-RPC from host environment.
The js bridge is heavily based on the code of our gopls wasm port.

Why no stdio?

• Because by default, there is no stdin implementation in browsers and getting a reliable stdin implementation on JS might be a complex task.

Where this will be used?

• Goal of this PR is to introduce LSP support in Gno Playground

Are there any examples?

• There is a bare-minimum embedding example in internal/js/example directory.