docs(service-worker): add UpdateActivated/AvailableEvent to the public API (#23138)

PR Close #23138

packages/service-worker/src/index.ts

@@ -14,6 +14,7 @@
 * found in the LICENSE file at https://angular.io/license
 */
 
+export {UpdateActivatedEvent, UpdateAvailableEvent} from './low_level';
 export {ServiceWorkerModule} from './module';
 export {SwPush} from './push';
-export {SwUpdate} from './update';
+export {SwUpdate} from './update';