build: Reintroduce icons to dist images-theme CSS files
build: Reintroduce icons to dist images-theme CSS files

Got lost in Ifcdfb8d19822.

Bug: T209131
Change-Id: I19e7435b3ccbb3f76f1e2b381b551b1ead4d23cc

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui