turn service worker back on

src/index.js

@@ -22,7 +22,7 @@ ReactDOM.render(
 // If you want your app to work offline and load faster, you can change
 // unregister() to register() below. Note this comes with some pitfalls.
 // Learn more about service workers: https://cra.link/PWA
-serviceWorkerRegistration.unregister();
+serviceWorkerRegistration.register();
 
 // If you want to start measuring performance in your app, pass a function
 // to log results (for example: reportWebVitals(console.log))