Improve dropdown menu keyboard navigation (#11491)

* Allow selecting menu items with the space bar in status dropdown menus

* Fix modals opened by keyboard navigation being immediately closed

* Fix menu items triggering modal actions

* Add Tab trapping inside dropdown menu

* Give focus back to last focused element when status dropdown menu closes

app/javascript/mastodon/containers/dropdown_menu_container.js

@@ -20,7 +20,7 @@ const mapDispatchToProps = (dispatch, { status, items }) => ({
     }) : openDropdownMenu(id, dropdownPlacement, keyboard));
   },
   onClose(id) {
-    dispatch(closeModal());
+    dispatch(closeModal('ACTIONS'));
     dispatch(closeDropdownMenu(id));
   },
 });