Add not worth mentioning initial skeleton for testing using pytest

[yarikoptic]

Would not test much if at all, but at least would try to install/import across all OSes and Python versions.

ref #1

edit: I also pushed as master to my clone so that action is executed... can be observed on https://github.com/yarikoptic/refuse/actions .

[yarikoptic]

both windows and OSX runs aren't happy so I will disable them for now since it annoys me to receive all the failing notifications emails ;-)