Add locale for en-ZA

[girtu]

Please can you prove a locale for South Africa (en-ZA) - ref: https://www.gov.za/about-sa/public-holidays#2022
All holidays are Nation-wide and have the date fixed except Good Friday which is dependent and on the western Easter date, and Family Day which is Easter Friday + 3
NB if holiday falls on a Sunday, then following Monday is also a holiday. e:g 2022-05-02 and 2023-09-25

2022

2022-01-01 New Year's Day
2022-03-21 Human Rights Day
2022-04-15 Good Friday
2022-04-18 Family Day
2022-04-27 Freedom Day
2022-05-01 Workers' Day
2022-05-02 Workers' Day (observed)
2022-06-16 Youth Day
2022-08-09 National Women's Day
2022-09-24 Heritage Day
2022-12-16 Day of Reconciliation
2022-12-25 Christmas Day
2022-12-26 Day of Goodwill

2023

2023-01-01 New Year's Day
2023-01-02 New Year's Day (observed)
2023-03-21 Human Rights Day
2023-04-7 Good Friday
2023-04-10 Family Day
2023-04-27 Freedom Day
2023-05-01 Workers' Day
2023-06-16 Youth Day
2023-08-09 National Women's Day
2023-09-24 Heritage Day
2023-09-25 Heritage Day (observed)
2023-12-16 Day of Reconciliation
2023-12-25 Christmas Day
2023-12-26 Day of Goodwill

Thanks

[lauft]

@girtu I created PR #80 for this.

There is one open question about those compensatory holidays which needs to be resolved before merging. Could you take a look at it?