Rename themes -> flavours ? ?

app/javascript/flavours/glitch/service_worker/entry.js

@@ -0,0 +1,10 @@
+import './web_push_notifications';
+
+// Cause a new version of a registered Service Worker to replace an existing one
+// that is already installed, and replace the currently active worker on open pages.
+self.addEventListener('install', function(event) {
+  event.waitUntil(self.skipWaiting());
+});
+self.addEventListener('activate', function(event) {
+  event.waitUntil(self.clients.claim());
+});