Update Sri Lankan holidays - Year 2024

[Dilshan-H]

• Added government holidays (Public and Bank Holidays) in Sri Lanka for the year 2024
• Source data: Department of Government Printing

[inson1]

@Dilshan-H SMT apps were sold. Fork is here https://github.com/FossifyOrg Please create PR there

[Dilshan-H]

@inson1 Thanks for the heads up. I will create the PR & my future contributions there for sure. It's really sad to see this happening to open source projects anyway.