code: function appendApiUrlParam(fullUrl, apiUrl) {
      let appendedUrl = fullUrl;
  
      if (typeof apiUrl === 'string') {
          if (fullUrl.indexOf('?') === -1) {
              appendedUrl += '?';
          } else {
              appendedUrl += '&';
          }
  
          appendedUrl += 'apiUrl=';
          // trim trailing slash from URL
          appendedUrl += apiUrl.slice(-1) === '/' ? apiUrl.slice(0, -1) : apiUrl;
      }
  
      return appendedUrl;
  }
docs: Append the GitHub "apiUrl" param onto the URL if necessary.
  @param fullUrl
  @param apiUrl
  @returns {String}