* Use lesser-known DT features to skip behaviors not referenced
in the user keymap
* Update the behaviors to skip code if no nodes found.
* Remove some empty config/data structs where unused in
behaviors.
* Use extra comptible = "zmk,behavior-global" to add
behaviors to global bindings for event notification.
* Implement mod-tap, as a keymap binding and global one
to skip tap if other keycode pressed while held.
