Add windows testing to GitHub Actions

[cthoyt]

Closes #166

[cthoyt]

@lvermue it looks like the windows configuration works. You can check it out in its own workflow, but I guess this needs to be copied twice into tests.yml and tests_master.yml, right?

[cthoyt]

@lvermue also it's quite slow. I wonder if there's any caching we can do to make these anaconda builds faster

[lvermue]

@cthoyt Is there a reason you install a new conda instance and aren't using the default one that comes with the Github Actions virtual environment pre-installed?

[lvermue]

https://github.com/conda-incubator/setup-miniconda#conda-incubatorsetup-miniconda Apparently they try to locate the pre-installed ones. So this shouldn't be the reason for the slowness 🤷‍♂️

[lvermue]

@lvermue also it's quite slow. I wonder if there's any caching we can do to make these anaconda builds faster

As written here #194 (comment), the Github Action virtual environments come with Conda pre-installed. The only way to have everything pre-installed would be to have our own instances, so maybe in the future 😅

[lvermue]

@PyKEEN-bot Can you attest this code?

[lvermue]

@PyKEEN-bot Once more. Can you attest this code?