Use button instead of span

Author: bechir

templates/form/fields.html.twig

@@ -11,9 +11,9 @@
     <div class="input-group date" data-toggle="datetimepicker">
         {{ block('datetime_widget') }}
         <div class="input-group-append">
-            <span class="btn btn-outline-secondary">
+            <button type="button" class="btn btn-outline-secondary">
                 <span class="fa fa-calendar" aria-hidden="true"></span>
-            </span>
+            </button>
         </div>
     </div>
 {% endblock %}