Add a Windows runner for the CI

[pablo-de-andres]

Sometimes OSP-core's installation in Windows behaves differently that Linux's, producing unexpected errors. In order to detect this, CI should be executed with a Windows runner.

Since Windows Docker images require a Windows host, we can use one of GitHub's hosted runners until we can set up our own Windows machine.

Given the licensing restrictions stated here, a good choice would be to run the CI on every commit to dev (rather than on every commit in a PR)