Kicad: update PCB for keyboard 100x100 minif4 36-key

Changelog:
- Update per the schematic:
  - e.g. fix issue from rev2021.1:
    - add LVC,
    - adjust position of top-right hole for M2 spacer.
  - add breakout pins for RGB in/out.
  - use the other 5V, 3V3, GND pins of the minif4.
- Use thinner traces for signal traces.
- Route so as to maximize the GND zone fill on back copper layer,
  try keep signal traces far apart.

Author: rgoulter