feat: code split & use react helmet

lib/core/clientEntry.js

@@ -0,0 +1,19 @@
+import React from 'react';
+import {BrowserRouter} from 'react-router-dom';
+import ReactDOM from 'react-dom';
+
+import App from './App';
+import prerender from './prerender';
+import routes from '@generated/routes'; // eslint-disable-line
+
+// Client side render (e.g: running in browser) to become single-page application (SPA)
+if (typeof window !== 'undefined' && typeof document !== 'undefined') {
+  prerender(routes, window.location.pathname).then(() => {
+    ReactDOM.render(
+      <BrowserRouter>
+        <App />
+      </BrowserRouter>,
+      document.getElementById('app')
+    );
+  });
+}