Add web client using WebSocket

[youngjoon-lee]

There are many ways to build web clients as mentioned in https://connectivity.libp2p.io.
At the beginning, I wanted to build an web client using WebRTC that is supported by rust-libp2p.

But, I've found an easier example: https://github.com/vincev/wasm-p2p-chat based on WebSocket (better supported by rust-libp2p currently, compared to WebRTC), which is based on https://github.com/vincev/libp2p-websys-transport (written by the same author with the websocket example). This libp2p-websys-transport will replace the official libp2p-wasm-ext in the rust-libp2p by the libp2p team: libp2p/rust-libp2p#3611. So, it would be worth investigating this way for now.

After getting familiar with this websocket way, I'll try to use WebRTC as well.

[youngjoon-lee]

We cannot proceed because libp2p-gossipsub isn't compiled for wasm-unknown-unknown, as mentioned in https://github.com/mriise/libp2p-wasm-chat/blob/4417083a7a1a3ed4ddcfe33d4f5fa6bb64d25c04/Cargo.toml#L32.

error[E0432]: unresolved import `libp2p::gossipsub`
  --> jiri-web/src/main.rs:11:5
   |
11 |     gossipsub, identity, noise,
   |     ^^^^^^^^^ no `gossipsub` in the root

That was why the https://github.com/vincev/wasm-p2p-chat was written using only floodsub, not gossipsub.

I also tried to build https://github.com/mriise/libp2p-wasm-chat that supports gossipsub by using the local clone of rust-libp2p as an workaround for wasm-unknown-unknown. But it wasn't compiled well, as complained in mriise/libp2p-wasm-chat#1.

I guess that this issue will be resolved by libp2p/rust-libp2p#2653, because I've got a wasm-timer related error when referring to the local clone of libp2p-gossipsub, as mentioned in https://github.com/mriise/libp2p-wasm-chat/blob/4417083a7a1a3ed4ddcfe33d4f5fa6bb64d25c04/Cargo.toml#L32.

All of these efforts have been commited in the client branch.