Separate "Release notes" from the "4.0 Announcement".

While the latter is part of the docs, the "Release notes" are linked to the GitHub "Releases" section; thus the added divider.

docs/_includes/navigation.html

@@ -27,14 +27,15 @@
             <span class="caret"></span>
           </a>
           <ul class="dropdown-menu">
+            <li{% if page.slug == "announcements-4.0" %} class="active"{% endif %}>
+              <a href="./announcements-4.0.html">4.0 Announcement</a>
+            </li>
+            <li class="divider"></li>
             <li>
               <a href="https://github.com/select2/select2/releases">
                 Release notes
               </a>
             </li>
-            <li{% if page.slug == "announcements-4.0" %} class="active"{% endif %}>
-              <a href="./announcements-4.0.html">4.0 Announcement</a>
-            </li>
           </ul>
         </li>
         <li{% if page.slug == "community" %} class="active"{% endif %}>