code: function requestBundles(requestedLangs = navigator.languages) {
      const newLangs = negotiateLanguages(
        requestedLangs, availableLangs, { defaultLocale }
      );
  
      const bundles = newLangs.map(
        lang => new ResourceBundle(lang, resIds)
      );
  
      return Promise.resolve(bundles);
    }
docs: This function is called by `Localization` class to retrieve an array of `ResourceBundle`s.