NickiForte

Add `include_sundays` flag to `country_holidays()`

3

## Feature Request ### Description The `include_sundays` flag is already available in country classes for some countries, as e.g. Sweden: https://github.com/vacanza/holidays/blob/df5c0bc6baf08677d145fefd9041d11990455d75/holidays/countries/sweden.py#L39 It would be of great help if this flag...