Add Mac and Windows support

[jacobtomlinson]

Which project are you reporting a bug for?

kr8s

What happened?

CI here only runs on Ubuntu, so therefore we can only guarentee linux support at the moment. However, issues are starting to pop up with Windows or Mac specific bugs (#365, #380).

It feels like time to officially add support for those platforms. However I am concerned by the number of CI jobs we already have given that we test all supported Python versions against all supported Kubernetes versions. Adding an OS dimension will triple the number of jobs running and new dimensions is a slippery slope towards a combinatorial explosion.

Perhaps a good first step is to test only the latest supported Python and Kubernetes on Windows and Mac.

Anything else?

No response