Request: support WebSocket proxy

Request to support WebSocket since I'm pretty its not supported by the proxy.

Try these settings:

```toml
[tools.lustre.dev]
proxy = [{ from = "/ws", to = "ws://localhost:8080/ws" }]
```

And these settings (just in case):

```toml
[tools.lustre.dev]
proxy = [{ from = "/ws", to = "http://localhost:8080/ws" }]
```

Both doesn't work and returns HTTP 500.

Thanks.