getBase64(url, mimeType) {
    var decodededUrl = window.decodeURIComponent(url.substr(1)); // Remove first slash

    var entry = this.zip.file(decodededUrl);

    if (entry) {
      mimeType = mimeType || mime.lookup(entry.name);
      return entry.async("base64").then(function (data) {
        return "data:" + mimeType + ";base64," + data;
      });
    }
  }
Get a base64 encoded result from Archive by Url
@param  {string} url
@param  {string} [mimeType]
@return {string} base64 encoded