code: function transformExtNameElement(element) {
      let {attribs: attrs} = element;
      let src = attrs && attrs.src;
  
      if (src) {
          attrs.src = src.replace(/\.wxml$/i, '.swan');
      }
  }
docs: src 引入 后缀转换: import and inlcude
  
  @param  {Object} element element