chore: add robots file

src/app/robots.ts

@@ -0,0 +1,15 @@
+import { siteConfig } from "@/config/site";
+import type { MetadataRoute } from "next";
+
+/**
+ * https://nextjs.org/docs/app/api-reference/file-conventions/metadata/robots
+ */
+export default function robots(): MetadataRoute.Robots {
+  return {
+    rules: {
+      userAgent: "*",
+      allow: "/",
+    },
+    sitemap: `${siteConfig.url}/sitemap.xml`,
+  };
+}