Use tungstenite instead of websocket-rs

The websocket-rs library uses outdated versions of tokio and futures-rs and the maintainers recommend using tungstenite instead.

ssam_openqa uses synchronous, blocking IO for the most part, however tungstenite can only be used via async_tungstenite with an async runtime (or tokio-tungstenite, another option). I chose tokio here as the most popular, async-std is also supported but smol is not.

Release binary size is 1.7MB after this change - slightly smaller than before \o/

Fixes #14 (closed)