Timeout for Serial Number
Plugin still works but this always appears in Homebridge logs. I can still control the vacuum but curious about this error. Thanks in advance!

```
ERR getSerialNumber | Failed getting the serial number. Error: Call to device timed out
    at Timeout.retry [as _onTimeout] (/usr/local/lib/node_modules/homebridge-xiaomi-roborock-vacuum/miio/lib/network.js:519:23)
    at listOnTimeout (internal/timers.js:554:17)
    at processTimers (internal/timers.js:497:7) {
  code: 'timeout'
}
```