- Remove background-color from header and footer in inverse cards (fixes#19841)
- Update border override for header and footer in cards; only need to declare a new color
- Update the selector for targetting blockquote footers in cards
I'm aware that currently cards are a lot simpler than buttons right now
but this may change in future and it feels cleaner to be able to create
new card styles without needing to know the internals of how they're
implemented.
Mark Otto