Added a link to the system status page

Changed the footer headings to better reflect what you get there...

app/templates/admin_template.html

@@ -83,14 +83,15 @@
     <div class="footer-categories-wrapper">
       <div class="grid-row">
         <div class="column-one-third">
-          <h2>Contact</h2>
+          <h2>Support</h2>
           <ul>
             <li><a href="{{ url_for('main.feedback') }}">Support and feedback</a></li>
             <li><a href="https://ukgovernmentdigital.slack.com/messages/govuk-notify">Chat with the Notify team</a></li>
+            <li><a href="https://status.notifications.service.gov.uk">System status</a></li>            
           </ul>
         </div>
         <div class="column-one-third">
-          <h2>Help</h2>
+          <h2>About</h2>
           <ul>
             <li><a href="{{ url_for("main.terms") }}">Terms of use</a></li>
             <li><a href="{{ url_for("main.trial_mode") }}">Trial mode</a></li>