Add rudimentary GitHub workflow for tests on Windows and Ubuntu
Add rudimentary GitHub workflow for tests on Windows and Ubuntu

The Windows one, in particular, is valuable, since it allows
developers who otherwise have limited access to Windows, to test
Windows-related issues.

It might perhaps be nice to cache the virtualenv, if possible?

Stvad/CrowdAnki,Stvad/CrowdAnki,Stvad/CrowdAnki