Issue #3500401: Render other attributes in views_display_switch template.

Closes #3500401

src/Plugin/views/area/DisplaySwitch.php

@@ -230,6 +230,9 @@ class DisplaySwitch extends AreaPluginBase {
     return [
       '#theme' => 'views_display_switch',
       '#links' => $links,
+      '#attributes' => [
+        'class' => ['views-display-switch'],
+      ],
     ];
   }