Holidays for the whole class

[SelectLOL1]

Discussed in #187

^{Originally posted by SelectLOL1 September 22, 2021}
Hello, first of all, thanks for this amazing open-source project.

My questions is: How can I add holidays for the whole schoolclass? Holidays that I add seem to be visible only for me.

Thank you very much and greetings
SelectLOL