Layers support

[ivanjermakov]

Actions:

• DF(layer) - Set the base (default) layer
• MO(layer) - Momentarily turn on layer when pressed (requires KC_TRNS on destination layer)
• OSL(layer) - Momentarily activates layer until a key is pressed. See One Shot Keys for details.
• LM(layer, mod) - Momentarily turn on layer (like MO) with mod active as well.
• LT(layer, kc) - Turn on layer when held, kc when tapped
• TG(layer) - Toggle layer on or off
• TO(layer) - Turns on layer and turns off all other layers, except the default layer
• TT(layer) - Normally acts like MO unless it's tapped multiple times, which toggles layer on