change color when card is highlighted

I didn't notice the highlighted part when changing DefaultCardBackground. Thanks to dimkard (from kirigami matrix) it was "brought to light" and so I made this MR.

Something i noticed in discover is that when directly going into Applications section it already highlights the first application as seen below. The reason is why i am bringing this up is because I don't know if this is a problem I made or it's just kirigami's implementation.