Add footer

* modify mdx layout

components/Footer.tsx

@@ -0,0 +1,18 @@
+import { FC } from 'react';
+
+const nowDay = new Date().getFullYear();
+
+const Footer: FC = () => {
+  return (
+    <>
+      <footer className="px-10">
+        <div className="h-[2px] bg-slate-500"></div>
+        <div className="py-4">
+          &copy; 2022-{nowDay} Powered by Next.js 💙 xfy
+        </div>
+      </footer>
+    </>
+  );
+};
+
+export default Footer;