Add KB article link to moderation emails

Author: acelaya

h/templates/emails/annotation_moderation_notification.html.jinja2

@@ -647,6 +647,17 @@ h4{
                                     </tbody>
                                   </table>
                                 {% endif %}
+                                <table border="0" cellpadding="0" cellspacing="0" width="100%" class="mcnButtonBlock" style="min-width:100%;">
+                                  <tbody class="mcnButtonBlockOuter">
+                                    <tr>
+                                      <td style="padding-top:18px; padding-right:18px; padding-bottom:18px; padding-left:18px;" valign="top" class="mcnTextContent">
+                                        <a href="https://example.com">
+                                          Click here to learn more about moderation in Hypothesis!
+                                        </a>
+                                      </td>
+                                    </tr>
+                                  </tbody>
+                                </table>
                               </td>
                             </tr>
                           </table>