Restructure code

src/ui/App.tsx

@@ -0,0 +1,17 @@
+import React from 'react';
+import logo from './logo.svg';
+import './App.css';
+
+function buttonFunctionality() {
+  alert('Button clicked!');
+}
+
+function App() {
+  return (
+    <div className="App">
+      <button onClick={buttonFunctionality}>Cool button</button>
+    </div>
+  );
+}
+
+export default App;