Add additional tips to maintenance error page

src/Templates/Core/Maintenance.phtml

@@ -1,5 +1,6 @@
 <?php /* vim: set colorcolumn= expandtab shiftwidth=2 softtabstop=2 tabstop=4 smarttab: */
 namespace BNETDocs\Templates\Core;
+use \CarlBennett\MVC\Libraries\Common;
 $title = 'Maintenance';
 $description = $this->getContext()->message;
 $_header_maintenance = true;
@@ -9,5 +10,25 @@ require('./Includes/header.inc.phtml'); ?>
     <h4 class="alert-heading"><?=$title?></h4>
     <p class="mb-0"><?=$description?></p>
   </div>
+  <div class="alert alert-primary" role="suggestion">
+    <p><strong>This page</strong> is currently unavailable from our website.</p>
+    <ul>
+      <li>You could try <strong>refreshing</strong> the page again later.</li>
+      <li>You might try loading this page from the
+        <a href="https://web.archive.org/web/*/<?=Common::relativeUrlToAbsolute(getenv('REQUEST_URI'))?>">
+          Wayback Machine Internet Archive</a>.
+      </li>
+<?php if (isset(Common::$config) && isset(Common::$config->discord) && isset(Common::$config->discord->invite_code)) { ?>
+      <li>You could use <a href="https://discord.gg/<?=Common::$config->discord->invite_code?>">Discord</a> to contact an administrator.</li>
+<?php } else { ?>
+      <li>You could use social media to contact an administrator.</li>
+<?php } ?>
+<?php if (isset(Common::$config) && isset(Common::$config->email) && isset(Common::$config->email->recipient_reply_to)) { ?>
+      <li>You could use an
+        <a href="mailto:<?=Common::$config->email->recipient_reply_to[1]?> &lt;<?=Common::$config->email->recipient_reply_to[0]?>&gt;">email message</a>
+        to contact an administrator.</li>
+<?php } ?>
+  </ul>
+  </div>
 </div>
 <?php require('./Includes/footer.inc.phtml'); ?>