Update frontend.jsx to use new React root API

The 'frontend.jsx' file under 'admin-settings' in the assets/js directory now uses the new React root API for rendering. The root API creates a root from a container and allows rendering operations to be scheduled over time. Instead of rendering directly in the component, a constant container is declared and then a root is created from this container for the rendering process.

assets/js/admin-settings/frontend.jsx

@@ -4,9 +4,11 @@ import ReactDOM from 'react-dom';
 // Components.
 import AdminSettings from './index';
 
-ReactDOM.render(
+const container = document.getElementById('apple-news-options__page');
+const root = ReactDOM.createRoot(container);
+
+root.render(
   <StrictMode>
     <AdminSettings />
   </StrictMode>,
-  document.getElementById('apple-news-options__page'),
 );