Add 'utils' module export (#410)

Export core utils and assets used by RWP in /utils.
Add serviceWorkerActivated() utility promise.

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Co-authored-by: emma <hi@emma.cafe>

src/swmanager.ts

@@ -153,3 +153,15 @@ export class SWManager {
     `;
   }
 }
+
+export async function serviceWorkerActivated() {
+  if (navigator.serviceWorker.controller) {
+    return;
+  }
+
+  await new Promise<void>((resolve) => {
+    navigator.serviceWorker.addEventListener("controllerchange", () => {
+      resolve();
+    });
+  });
+}