Change how theme style packs are loaded

Load the `common` style pack, and then charge the style pack for the current
skin, independent from any selected JS pack.

app/javascript/flavours/glitch/packs/application.js

@@ -1,8 +1,12 @@
 import 'packs/public-path';
+
+import { start } from 'flavours/glitch/common';
 import { loadLocale } from 'flavours/glitch/locales';
 import main from "flavours/glitch/main";
 import { loadPolyfills } from 'flavours/glitch/polyfills';
 
+start();
+
 loadPolyfills()
   .then(loadLocale)
   .then(main)