Code refactoring

Author: BobsProgrammingAcademy

frontend/src/layout/Header.js

@@ -1,4 +1,6 @@
 import PropTypes from 'prop-types';
+
+// Material UI
 import AppBar from '@mui/material/AppBar';
 import Button from '@mui/material/Button';
 import Box from '@mui/material/Box';