Attempt to return focus explicitly to dropdown trigger (#41365)

Co-authored-by: Mark Otto <mdo@heypierre.app>

js/src/dropdown.js

@@ -207,6 +207,9 @@ class Dropdown extends BaseComponent {
     this._element.setAttribute('aria-expanded', 'false')
     Manipulator.removeDataAttribute(this._menu, 'popper')
     EventHandler.trigger(this._element, EVENT_HIDDEN, relatedTarget)
+
+    // Explicitly return focus to the trigger element
+    this._element.focus()
   }
 
   _getConfig(config) {