Added experimental WebSocket transport support with basic WS and WSS functionality. This includes:

- WebSocket transport implementation with trio-websocket backend
- Support for both WS (WebSocket) and WSS (WebSocket Secure) protocols
- Basic connection management and stream handling
- TLS configuration support for WSS connections
- Multiaddr parsing for WebSocket addresses
- Integration with libp2p host and peer discovery

**Note**: This is experimental functionality. Advanced features like proxy support,
interop testing, and production examples are still in development. See
 https://github.com/libp2p/py-libp2p/discussions/937 for the complete roadmap of missing features.