Use BTN3 in the semicolon slot in the mouse mode layer
Use BTN3 in the semicolon slot in the mouse mode layer

This was just a test to see if adding BTN3 to some other key would
cause it to register as Button 3 in xev under Linux. It still shows up
as Button 2, and BTN2 still shows up as Button 3.

bgoodr/keyboard-firmware-build-util,bgoodr/keyboard-firmware-build-util