code: def register_blockquote_feature(features):
      
      feature_name = 'blockquote'
      type_ = 'blockquote'
      tag = 'blockquote'
  
      control = {
          'type': type_,
          'label': '❝',
          'description': 'Quote',
          'element': 'blockquote',
      }
  
      features.register_editor_plugin(
          'draftail',
          feature_name,
          draftail_features.BlockFeature(control)
      )
  
      features.register_converter_rule(
          'contentstate',
          feature_name,
          {
              'from_database_format': {tag: BlockElementHandler(type_)},
              'to_database_format': {'block_map': {type_: tag}},
          }
      )
      features.default_features.append(feature_name)
docs: Registering the `blockquote` feature, which uses the `blockquote` Draft.js block type,
      and is stored as HTML with a `<blockquote>` tag.