docs: fix meta assets of user guide (#11639)

www/apps/user-guide/app/sitemap.ts

@@ -0,0 +1,13 @@
+import { retrieveMdxPages } from "build-scripts"
+import type { MetadataRoute } from "next"
+import path from "path"
+import { config } from "../config"
+import { basePathUrl } from "../utils/base-path-url"
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  return retrieveMdxPages({
+    basePath: path.resolve("app"),
+  }).map((filePath) => ({
+    url: `${config.baseUrl}${basePathUrl(filePath)}`,
+  }))
+}