enable cors

Adding the snippet so that the sample is in sync with the docs.

Author: kengaderdus

index.js

@@ -37,9 +37,11 @@ const app = express();
 app.use(express.json()); 
 
 //enable CORS (for testing only -remove in production/deployment)
-app.use(cors({
-    origin: '*'
-}));
+app.use((req, res, next) => {
+    res.header('Access-Control-Allow-Origin', '*');
+    res.header('Access-Control-Allow-Headers', 'Authorization, Origin, X-Requested-With, Content-Type, Accept');
+    next();
+});
 
 app.use(morgan('dev'));