feat(behaviors): add usb MIDI behavior support

[SolidHal]

adds support for sending MIDI notes across 10 octaves adds support for sending MIDI control change codes adds MIDI behavior documentation

docs can be found at docs/docs/behaviors/midi.md

testing: example implementation on the btrfld keyboard here https://github.com/SolidHal/zmk/tree/btrfld/app/boards/shields/btrfld tested on both nice_nano_v2 and bluemicro840_v1 verified MIDI output using midisnoop https://linuxaudio.github.io/libremusicproduction/html/tools/midisnoop.html made a song using this :)