code: private function addBlockSection(ArrayNodeDefinition $rootNode)
      {
          $rootNode
              ->fixXmlConfig('block_theme')
              ->children()
                  ->arrayNode('block_themes')
                      ->prototype('scalar')->end()
                      ->example(['@App/block.html.twig'])
                  ->end()
              ->end()
          ;
      }
docs: Add block section.
  
  @param ArrayNodeDefinition $rootNode