seo: add robots.ts with sitemap reference

src/app/robots.ts

@@ -0,0 +1,14 @@
+import { MetadataRoute } from "next";
+
+export default function robots(): MetadataRoute.Robots {
+  return {
+    rules: [
+      {
+        userAgent: "*",
+        allow: "/",
+      },
+    ],
+    sitemap: "https://www.wilddragon.net/sitemap.xml",
+    host: "https://www.wilddragon.net",
+  };
+}