This example displays the text “Hello React!” in large, centered type. It demonstrates a minimal React 18 application structure using the UMD builds of React and ReactDOM, loaded directly from unpkg. The `App` component returns a simple `div` with a CSS class, and the `createRoot` API from `react-dom` renders that component into the `#root` element on the page. No external data sources or complex rendering logic appear in this starter code.