fix(WebWorker): Add @AngularEntrypoint to worker_app bundle

Closes #5588

Author: jteplitz

modules/angular2/platform/worker_app.ts

@@ -16,3 +16,4 @@ export {
 } from '../src/web_workers/shared/service_message_broker';
 export {PRIMITIVE} from '../src/web_workers/shared/serializer';
 export * from '../src/web_workers/shared/message_bus';
+export {AngularEntrypoint} from 'angular2/src/core/angular_entrypoint';