- Change await self._send_read_receipt to asyncio.create_task to avoid
blocking message dispatch on slow bridge responses (matches BlueBubbles
pattern). Up to 5s per-message latency eliminated.
- Update tests: assert_called_once_with instead of assert_awaited_once_with
since the receipt is now scheduled, not directly awaited.
- Add send_read_receipts documentation to whatsapp.md following the
BlueBubbles docs pattern.