Add WebSocket listener support (v1.2.0)

- Add listen() and stream() APIs for real-time hook delivery via WebSocket
- Add Result type (ack/accept/nack) shared across HTTP and WebSocket handlers
- Add ASGI/WSGI handler wrappers with Result dispatch
- Add auto-reconnection, heartbeat monitoring, bounded concurrency
- Add certifi-backed SSL context for websockets library compatibility
- Add websockets dependency (>=12.0)
- Add keywords to pyproject.toml

Release v1.1.0 — async hooks callbacks

Rename PyPI package to posthook-python