LEDs: add rainbow effects

[acheronfail]

Setting the headlights to Solid with white, and then setting the taillights to Rainbow Cycle allows users to replicate the Mullet effect from the Float package.

Using Rainbow Cycle on the front and the back replicates the "Rave" effect from the Float package.

~~Rainbow Fade has also been added, which was inspired by the Float package's "RGB Fade" effect.~~ Renamed to RGB Fade after using color_wheel.