weekOfWeekYear method
Returns the week number within the week year.
Implementation
int weekOfWeekYear([WeekYearConfig config = WeekYearConfig.iso]) {
final thursday = _getWeekThursday(config);
final firstWeekThursday = _firstWeekThursday(thursday.year, config);
return ((thursday.difference(firstWeekThursday).inDays) ~/ 7) + 1;
}