Request: Set icon color when entity is off

[Inrego]

Is your feature request related to a problem? Please describe.
I don't like the default colors of icons. I like that this card lets me change icon color, but it only changes color when the entity is off. I'd love an icon_off_color attribute as well.

Describe alternatives you've considered
I've considered setting it with card_mod, but having it as an option directly in the card here would be nice.