Add `embedded-io-async` Framer

[LimpidCrypto]

Overview

This PR adds a Framer that uses the embedded_io_async::Write and embedded_io_async::Read traits instead of the futures::Sink and futures::Stream traits. It makes it easier to use the WebSocket with TcpStreams implementing the embedded_io_async traits, like the embassy_net::TcpSocket. The Framer is behind the embedded-io-async feature.

Tests

I added an example using the Framer with the tokio::net::TcpStream wrapped in embedded_io_adapters::FromTokio as it's pretty straight forward and demonstrates the functionality sufficiently.

Todo

• [ ] Remove .devcontainer