Add notfound page

+import { Link } from "react-router-dom";
+
+function Notfound() {
+  return (
+    <>
+      <h1>404: Page Not Found</h1>
+      <h2>
+        <Link to="/">back to home</Link>
+      </h2>
+    </>
+  );
+}
+
+export default Notfound;