#11 Support UPDI programming

[Maximilian Gerhardt]

The fork https://github.com/Florin-Popescu/avarice contains some bleeding-edge expansions to avarice regarding programming / debugging microcontrollers with the UPDI interface. I think that's very cool and would eventually allow debugging of e.g. the Arduino Nano Every board with no extra debug-probe and those features should definitely be merged back. Maybe even a collaboration is possible?