dark mode and light mode in the display of the credentials

[Sakurann]

@leecam pointed out that it would be nice to have a dark and light versions for any images or colors specified in the display object of a credential. Is there support to add this functionality? one way to do this might be to have two objects with type light and dark (need to make sure it is backward compatible)

[ThierryThevenet]

On our side if the specs were implemented we would use them (display with background images)