Add Support for Kosovo

[kasgithub8]

Hello,

I was testing out the nuget package Nager.Holiday and the API when I noticed that Kosovo is missing.
Is Kosovo on the roadmap?
The data would be perfect because we were looking for a package that supports Germany, Greece, Spain, Bulgaria and Kosovo.

[edoniti]

+1 for this. here is the law regarding the public holidays in Kosovo https://gzk.rks-gov.net/ActDocumentDetail.aspx?ActID=2539