feat: Add ARIA role to the dropdown list (#95)

Co-authored-by: Michael Park <michael.park@canonical.com>

Author: yhontyk

canonical_sphinx/theme/templates/header.html

@@ -26,28 +26,32 @@
         {% endif %}
       </li>
 
-      <li>
-        <a href="#" class="p-navigation__link nav-more-links">More resources</a>
-        <ul class="more-links-dropdown">
-
+      <li class="nav-dropdown">
+        <a href="#" class="p-navigation__link nav-more-links"
+           id="more-resources-toggle"
+           aria-haspopup="true"
+           aria-expanded="false">
+          More resources
+        </a>
+        <ul class="more-links-dropdown" aria-labelledby="more-resources-toggle">
           {% if discourse %}
           <li>
             <a href="{{ discourse }}" class="p-navigation__sub-link p-dropdown__link">Discourse</a>
           </li>
           {% endif %}
-
+      
           {% if mattermost %}
           <li>
             <a href="{{ mattermost }}" class="p-navigation__sub-link p-dropdown__link">Mattermost</a>
           </li>
           {% endif %}
-
+      
           {% if matrix %}
           <li>
             <a href="{{ matrix }}" class="p-navigation__sub-link p-dropdown__link">Matrix</a>
           </li>
           {% endif %}
-
+      
           {% if github_url %}
           <li>
             <a href="{{ github_url }}" class="p-navigation__sub-link p-dropdown__link">GitHub</a>