Migrate Modern theme to separate Flavour

app/javascript/flavours/glitch/packs/common-modern.js

@@ -0,0 +1,8 @@
+import 'packs/public-path';
+import { start } from '@rails/ujs';
+import 'flavours/glitch/styles/modern.scss';
+
+start();
+
+//  This ensures that webpack compiles our images.
+require.context('../images', true);