Handle hotplugging
Draggy currently scans for devices on start, then opens an event loop for each device. Removing a device causes an error, and new devices aren't detected while draggy is running, requiring a restart. It would be nice to have hotplugging support to gracefully handle adding and removing devices.
- Handling removal of devices shouldn't throw an error
- Removed devices should clean up the respective "surrogate" devices
- A separate loop will be required to scan for new devices