(theme) add support for custom theme.js hook (3), login page missing jQuery...

src/etc/inc/authgui.inc

@@ -408,6 +408,9 @@ function display_login_form($Login_Error = '')
 
     <link href="/ui/themes/<?= $themename ?>/build/css/main.css" rel="stylesheet">
     <link href="/ui/themes/<?= $themename ?>/build/images/favicon.png" rel="shortcut icon">
+    <!-- JQuery -->
+    <script type="text/javascript" src="/ui/js/jquery-1.12.0.min.js"></script>
+
 <?php
     if (file_exists("/usr/local/opnsense/www/themes/".$themename."/build/js/theme.js")):?>
     <script type="text/javascript" src="/ui/themes/<?=$themename?>/build/js/theme.js"></script>