Added user button and menu.

components/Account.js

@@ -0,0 +1,15 @@
+import React from 'react';
+import { useSelector } from 'react-redux';
+import Page from './Page';
+import styles from './Account.module.css';
+
+export default function Account() {
+  const user = useSelector(state => state.user);
+  return (
+    <Page>
+      <h2>Account</h2>
+      <div className={styles.label}>username</div>
+      <div>{user.username}</div>
+    </Page>
+  );
+}