chore(react): add custom web index

web/src/index.js

@@ -0,0 +1,17 @@
+import { hydrateRoot, createRoot } from 'react-dom/client'
+
+import App from './App'
+/**
+ * When `#redwood-app` isn't empty then it's very likely that you're using
+ * prerendering. So React attaches event listeners to the existing markup
+ * rather than replacing it.
+ * https://reactjs.org/docs/react-dom.html#hydrate
+ */
+const redwoodAppElement = document.getElementById('redwood-app')
+
+if (redwoodAppElement.children?.length > 0) {
+  hydrateRoot(redwoodAppElement, <App />)
+} else {
+  const root = createRoot(redwoodAppElement)
+  root.render(<App />)
+}