Feature Request: Add option to Entity Rainbowifier to use unique shader for use with more entities

[MikosDrafle]

Add an option to the Entity Rainbowifier that enables the use of a shader that acts like the Rainbow Spinner shader, except it modifies the entire entity's visuals. This could be useful for rainbowifiers that use SolidTiles or BackgroundTiles, and the Rainbow Spinner Area Controller from Maddie's Helping Hand to create multi-colored tiles with ease.