update ad script and update resources

_data/resources-plugins-form.yml

@@ -78,6 +78,11 @@
   description: A jQuery multiselect plugin based on Bootstrap.
   supports:    bs3
 
+- name:        Bootstrap Select Dropdown
+  link:        https://thompsonsj.com/bootstrap-select-dropdown/
+  description: A jQuery plugin for Bootstrap 4 that converts select and multiselect elements to dropdowns.
+  supports:    bs4
+
 - name:        Bootstrap Toggle
   link:        http://www.bootstraptoggle.com/
   description: Bootstrap Toggle is a highly flexible Bootstrap plugin that converts checkboxes into toggles

_includes/ad.html

@@ -1 +1 @@
-<script async type="text/javascript" src="//cdn.carbonads.com/carbon.js?zoneid=1673&serve=C6AILKT&placement=startbootstrapcom" id="_carbonads_js"></script>
+<script async type="text/javascript" src="//cdn.carbonads.com/carbon.js?serve=CKYIP53E&placement=startbootstrapcom" id="_carbonads_js"></script>

_includes/footer.html

@@ -7,7 +7,7 @@
       <h2>Want more Bootstrap themes &amp; templates?</h2>
       <h5>Subscribe to our mailing list to receive an update when new items arrive!</h5>
       <div id="mc_embed_signup">
-        <form role="form" action="https://startbootstrap.us3.list-manage.com/subscribe/post?u=531af730d8629808bd96cf489&amp;id=afb284632f" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" target="_blank" novalidate>
+        <form role="form" action="https://startbootstrap.us3.list-manage.com/subscribe/post?u=531af730d8629808bd96cf489&amp;id=afb284632f" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" target="_blank" novalidate="novalidate">
           <div class="input-group input-group-lg">
             <input type="email" name="EMAIL" class="form-control" id="mce-EMAIL" placeholder="Email address...">
             <span class="input-group-btn">