[Feature Request] Invoke `set-rgb` without overriding the layer colors

[noidwasavailable]

It would be lovely to have a functionality where the original colors of the layers are preserved, and only the keys targeted by the set-rgb command are changed.

For example, a layer by default has #FF0000 on all keys.

After kontroll set-rgb --led 0 --color #00FF00, all keys are red, except the top-left key on the left board of the connected Voyager, which turns to green.