this makes LS(LEFT_CONTROL) work as if shift and control were both
pressed explicitly. Previously, the left shift would have been released
as soon as another key was pressed. The implicit behavior is useful in
case of LS(NUMBER_1) when rolling over to other keys.
Also see #361.
Key release events released keys on the wrong layer if the 'top layer'
was not &trans above the &mo key.
base <&mo 1>
layer 1 <&kp B>
This was caused by overwriting
`zmk_keymap_active_behavior_layer[position]` after the &mo key was
handled.