Run the tests on Windows

[maximlt]

This site lets people download a ZIP of each example so they can run it locally. Since most visitors are on Windows, we should make sure the examples run well on this platform, too. Currently, projects are tested and built by default on ubuntu-latest. They have the option to declare a specific runner by setting gh_runner in the project file (to e.g. macos-latest). There's no project using that feature at the moment (it might have been required to run a project that needed more memory on macos-latest). An option would be to run the test (not the build, to keep it simple) of a project by default on ubuntu-latest and windows-latest, unless it declares gh_runner.