ErgoDox EZ ⌘ layout in 2 stages

Stage 1: 2 layers:

• [x] stage 1 design
• [ ] set modifiers to thumb cluster
• [ ] combine FN-# layer and mouse layer
• [ ] FN caps-lock for now?

Stage 2:

• [ ] sticky modifiers: press both modifiers (left and right) to get sticky modifiers, press again to release, e.g. Left-Shift + Right-Shift = CAPS Lock
• [ ] tap-and-hold for temp layers?