Add Mobile page containing About

client/src/components/mobile/Mobile.js

+import React from 'react';
+import Card from 'react-bootstrap/Card';
+import About from '../about/About';
+
+export default function Mobile() {
+  return (
+    <Card className="vh-100 min-vh-100 border-0">
+      <About message={'Please use a desktop browser to access this website.'} />
+    </Card>
+  );
+}