Native Docker image support for Windows (WCOW/WSL)

[gesellix]

See the comment at #222 (comment):
It would be nice to build a native Windows container as part of the multi-platform build/release.

buildx currently doesn't support Windows containers out of the box, so some custom build steps will be necessary. See docker/build-push-action#18 for details. There are workarounds possible, see https://github.com/docker-client/echo-server/blob/main/.github/workflows/release.yml#L89 for an example in one of my personal projects.

Windows native containers would require Windows native shell scripts, so there's more to do before going all in on Windows native containers.