Add alter hook for enabling the sidebar tray

Hi,

While using the quick_node_clone module in combination with the Thunder Admin theme, I saw that the advanced vertical tabs where not looking correctly.

Dove in the theme and found that this was causing the vertical tabs to look correctly:

/**
 * Checks if advanced vertical tabs should apply on this route.
 *
 * @return bool
 *   Should apply or not.
 */
function _thunder_admin_apply_advanced_vertical_tabs() {

  $route = Drupal::service('current_route_match');
  switch ($route->getRouteName()) {
    case 'entity.taxonomy_term.add_form':
    case 'node.add':
    case 'entity.node.content_translation_add':
      return TRUE;
  }

  if ($route->getRouteObject()->getDefault("_entity_form")) {
    return TRUE;
  }

  return FALSE;
}

Quickfix
Will provide a patch where the quick node clone route is added as a quickfix,

Long term fix
I think we have to make it possible that (non core) routes can be added by a hook or something else, therefor giving some more flexibility from external contrib routes.