Adds Glove80's status indicator using RGB underglow support. Requires ZMK
PR#999 and PR#1243.
The underglow status is able to show layer state, battery levels,
caps/num/scroll-lock, BLE and USB state. The underglow positions selected for
each of these indicators is configured using the new devicetree node
zmk,underglow-indicators, which takes an array of integer LED positions for each
feature.
