code: function registerExtension(name, extension, options, mergeConfig) {
    var params = name;
  
    if (!isObject(name)) {
      params = {};
      params[name] = {
        extension: extension,
        options: options
      };
    }
  
    each(params, function (v, name) {
      if (v) {
        var _extension = v.extension,
            _options3 = v.options;
  
        if (_extension) {
          extensions[name] = _extension;
        } else if (!mergeConfig) {
          extensions[name] = v;
        }
  
        if (mergeConfig) {
          if (!extensionConfig[name]) {
            extensionConfig[name] = _config();
          }
  
          assign(extensionConfig[name], _options3);
        } else {
          extensionConfig[name] = _config(_options3);
        }
      }
    }, false);
  }
docs: Register extension and also can batch add