Galene 0.6 support and cleanup

[erdnaxe]

• Add a new version field in the handshake message (Galene 0.6.0+).
• Improve Python typehints.
• Use 127.0.0.1 rather than localhost in README as using localhost might cause issues (IPv6?).
• Ignore chathistory events (no more warnings on join).
• Add pytest to GitHub Workflows.
• Add testing for Python 3.10.
• Add galene-stream.py entrypoint to the root of this repository to run the gateway without having to install the Python module.