[issue-267] Add GitHub Actions workflow

[armintaenzertng]

fixes #267

removing the CircleCI workflow

this makes even Windows working again :)

[maxhbr]

Actions are not yet running? maybe modify the on: to change this?

[armintaenzertng]

They do run on my branch: https://github.com/armintaenzertng/tools-python/actions

I have added pull_request as a trigger for the workflow, but I think we have to merge this first, as currently the pipeline is still trying to use CircleCI.

[maxhbr]

You mean "your fork", but that is good to know.