Updated POTFILES.in
Adwaita: border radiusses rationalization
Adwaita: slightly contrasting popover background
HighContrast: Drop settings.ini

The only setting in there is already the default behavior,
and the setting is deprecated and ignored anyway.
HighContrast: Add sass parsing script

Just a copy of what we have next door in Adwaita.
Drop gtk.gresource.xml

Theme resources are controlled from the (generated) .gresource.xml
file two stories up.
HighContrast: integrate in build machinery
inspector: Add HighContrast to built-in themes list