devel/py-dunamai: Add py-dunamai 1.12.0

Dunamai is a Python library and command line tool for producing dynamic,
standards-compliant version strings, derived from tags in your version control
system. This facilitates uniquely identifying nightly or per-commit builds in
continuous integration and releasing new versions of your software simply by
creating a tag.

WWW: https://github.com/mtkennerly/dunamai