Server wasm support

[Dreaming-Codes]

It would be beneficial for this library to support WebAssembly for the server, enabling its use as a backend for Cloudflare Workers and similar WebAssembly runtimes.

There's a related discussion about WebAssembly support in a library that uses this one, found at andogq/qubit#102.

[andogq]

One potential path forward is to put Server behind a (default) feature. This would allow it to be disabled, allowing the tokio/net feature to also be disabled, thus allowing Tokio to compile for wasm32-unknown-unknown.

The only other Tokio feature that may need additional massaging in order to remain within the set of Tokio features that support WASM is rt-multi-thread. This could similarly be a feature enabled by default.

If the maintainers have any other thoughts I'd be very interested to hear them, as this is a feature we'd really like to see in Qubit! Thanks :)