code: public function addRouteDefinitions(...$routes)
      {
          foreach ($routes as $route) {
              if (is_callable($route)) {
                  $route($this->app);
              } elseif (is_string($route)) {
                  $callable = new $route();
                  $callable($this->app);
              } else {
                  throw new \InvalidArgumentException('Unsupported type for the route');
              }
          }
  
          return $this;
      }
docs: Add application route(s).
  The only requirement: $routes can be a callable or a string for a class name.
  A $routes parameter may not be necessarily an instance of Kod\BootstrapSlim\RouteDefinitions.
  @param $routes ...    Unlimited number of routes definitions.
  @return static
  @throws \InvalidArgumentException