Expose an option to color light slider based on entity, false would default to CSS variable.

[fcassata]

Playing with the new CSS variables in the beta, and I notice I can't set the light slider color, because it always gets the color of the entity from the getIconColor functions.

My request is to fix this by exposing a boolean YAML setting for the button card, something like entity_color: true/false. True would be the current implementation. False would default to the accent-color CSS variable, or if not set, a defined default color.

[fcassata]

The attached video shows how this fixes the flashing issue where custom CSS colors need to be applied after rendering (the lower sliders, cover cards), vs the top ones that don't expose CSS variables and must be applied after rendering the elements.

css_test.mov