Add new Slovenian identifier type - Unique Master Citizen Number
In Slovenia we have a special personal identifier called EMŠO - Enotna matična številka občana (Unique Master Citizen Number). This identifier is defined in "stdnum" since version 1.18: https://arthurdejong.org/python-stdnum/doc/1.18/stdnum.si.emso
The EMŠO is used for uniquely identify persons including foreign citizens living in Slovenia, It is issued by Centralni Register Prebivalstva CRP (Central Citizen Registry).
It would be great if we can add it to identifiers. I'm happy to contribute a merge request.