Add boilerplate.

app/app.tsx

@@ -0,0 +1,27 @@
+/// <reference path="../typings/react/react.d.ts" />
+
+import React = require('react');
+
+class DemoProps {
+  public name: string;
+}
+
+class Demo extends React.Component<DemoProps, any> {
+  constructor(props: DemoProps) {
+    super(props);
+  }
+  render() {
+    return (
+      <div>Hello {this.props.name}!</div>
+    );
+  }
+}
+
+function render() {
+  React.render(
+    <Demo name="World" />,
+    document.getElementById('app')
+  );
+}
+
+render();