:sparkles: Add support for Elgato Key Light

[rneswold]

This issue tracks progress of the Elgato driver for supporting Elgato Key Lights.

[rneswold]

Since this is the first bulb device, we should come up with a common set of devices that all bulb devices should support.

[rneswold]

This doesn't have to be coordinated with a release of DrMem. New drivers can be introduced at any time (although it will require drmemd's version to go up a patch level.)