Restructure docs (#11620)

docs/src/pages/index.js

@@ -0,0 +1,15 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import React from "react";
+import { Redirect } from "@docusaurus/router";
+
+export default function Home() {
+  return <Redirect to="docs/get_started/introduction" />;
+}