Update layout

Author: jonels-msft

docs/_templates/layout.html

@@ -11,12 +11,12 @@
 {%- block footer %}
   {%- if not READTHEDOCS %}
     <div class="rst-versions" data-toggle="rst-versions" role="note" aria-label="{{ _('Versions') }}">
-      <span class="rst-current-version" data-toggle="rst-current-version">
+      <button class="rst-current-version" aria-expanded="false" aria-controls="docs_versions" data-toggle="rst-current-version">
         <span class="fa fa-book"> Read the Docs</span>
         v: latest
         <span class="fa fa-caret-down"></span>
-      </span>
-      <div class="rst-other-versions">
+      </button>
+      <div class="rst-other-versions" id="docs_versions">
         <dl>
           <dt>{{ _('Versions') }}</dt>
           {%- if test_versions %}