keyboard: Implement HID keyboard

TODO:

- [x] Basic keyscan
- [x] Send UP/LEFT/RIGHT/CAPS HID reports, DOWN to go into bootloader
- [x] Can go into D2 (tested on Linux)
- [x] Can wake host (remote wakeup)
- [ ] Both serial and HID keyboard as composite device
- [ ] Key Debouncing
- [ ] 1-Zone PWM backlight
- [ ] RGB backlight (needs new/modified Rust driver)
- [ ] Separate builds for different keyboard variants
- [ ] Measure and optimize scan frequency
- [ ] Implement full key matrix with all keys
- [ ] Implement second layer for FN (including FN lock)
- [ ] Persist brightness setting and FN lock through reset
- [ ] Media keys

Signed-off-by: Daniel Schaefer <dhs@frame.work>

Author: JohnAZoidberg

Cargo.lock

@@ -34,6 +34,8 @@ usbd-serial.workspace = true
 usbd-hid.workspace = true
 fugit.workspace = true
 
+usbd-human-interface-device = "0.3.1"
+
 [dependencies.fl16-inputmodules]
 path = "../fl16-inputmodules"
 features = ["keyboard"]