Add Javanese calendar

[azlkiniue]

Came here from the Tom Scott newsletter, thank you for your work!

I have suggestion for adding javanese calendar. There are some references that seems can help:

• https://en.wikipedia.org/wiki/Javanese_calendar
• https://github.com/beaudu/weton presented in this article https://arxiv.org/abs/2012.10064
• https://github.com/kalenderjawa/pustaka

[CodapopKSP]

Thank you for the suggestion and sources! I will add it to my to do list. It seems like a very lengthy calculation but I will be happy to add it to the Library.