feature(react): add demo of react

packages/demos/react/src/App.js

@@ -0,0 +1,24 @@
+import React, { Component } from 'react';
+import logo from './logo.svg';
+import './App.css';
+
+import PageOne from './pages/PageOne';
+
+import { Delegate, wc } from '@ionic/react';
+
+class App extends Component {
+  render() {
+    return (
+      <ion-app>
+        <ion-nav-controller ref={wc({}, {
+          delegate: Delegate
+        })}></ion-nav-controller>
+        <ion-nav ref={wc({},{
+          root: PageOne
+        })}></ion-nav>
+      </ion-app>
+    );
+  }
+}
+
+export default App;