Typos in code related to logging
In some logging statements, "unknown" has incorrectly become "unkown".

There are at least the following occurrences:

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L73

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L122

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L150

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L154

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L158

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L165

https://github.com/AlexGustafsson/homebridge-wol/blob/181965fb4ac8554509541fb59914e05a89da500f/lib/network-device.js#L171

A fix should correct all these occurrences.