feat: add async wasm feature to facade crate

[niklasad1]

This is useful when doing conditional compilation for supporting both ws-client and wasm from the jsonrpsee root crate instead having to import the jsonrpsee-wasm-client for the wasm stuff and jsonrpsee for rest of the clients.

See example here, it's a bit niche feature quite useful but we can also skip it because of technical debt of all different features.