getFirstDayOfWeek = () => {
    if (formatSettings === undefined) {
      formatSettings = (0, _InitialConfiguration.getFormatSettings)();
    }
    return formatSettings.firstDayOfWeek;
  }
Returns the first day of the week from the configured format settings or based on the current locale.
@public
@returns {Number} 0 (Sunday) through 6 (Saturday)