Adding reason_code during disconnect

[vicrem]

Hello, first I want to thank you for making it easy to use gmqtt with FastAPI!
Second is more of a wish than issue. I need a way to send reason_code during shutdown, so if possible, can you change to this?

async def mqtt_shutdown(self, reason_code=0) -> None:
    """Final disconnection for MQTT client, for lifespan shutdown."""
    await self.client.disconnect(reason_code)

Many thx
//Victor