Flashing firmware to LBX without manual build/VSCode

PlatformIO wasn't working for me on Arch Linux for some reason, so I used `arduino-cli` instead to flash it to my lbx. Thought I'd put it here for anyone else to use. I'm use this would work for any other Arduino based pad.

```shell
arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:avr:leonardo --input-file firmware.hex
```