docs: function SpineLoader(url, crossorigin)
  {
      EventTarget.call(this);
  
      /**
       * The url of the bitmap font data
       *
       * @property url
       * @type String
       */
      this.url = url;
  
      /**
       * Whether the requests should be treated as cross origin
       *
       * @property crossorigin
       * @type Boolean
       */
      this.crossorigin = crossorigin;
  
      /**
       * [read-only] Whether the data has loaded yet
       *
       * @property loaded
       * @type Boolean
       * @readOnly
       */
      this.loaded = false;
  }