add test components

src/index.tsx

@@ -0,0 +1,9 @@
+import * as React from "react";
+import * as ReactDOM from "react-dom";
+
+import Hello from "./components/Hello";
+
+ReactDOM.render(
+  <Hello name="TypeScript" enthusiasmLevel={10} />,
+  document.getElementById('root') as HTMLElement
+);