Source pill legibility issues
@feaneron pointed out some legibility issues with the source pills yesterday:
There is low contrast, particularly for the beta pill in light style and the flatpak pill in dark.
@exalm pointed out that we already have colours for the age ratings, which could be reused here. Presumable that is these lozenges:
https://gitlab.gnome.org/GNOME/gnome-software/-/blob/main/src/style.css#L461