Feature request description

Please add support for the "buildx build --push" and/or "buildx build --output=type=registry" flags which would ensure that the built image is pushed to the registry. According to the buildx reference, the --push flag is just shorthand for --output=type=registry. So IMHO implementing both these things would be ideal, but I will be happy with either one.

Suggest potential solution

A clear and concise description of what you want to happen.

Have you considered any alternatives?

When using the CLI manually, I can of course use a separate command to push the image, this feature would help in integration with other tools - I am using DevSpace CLI tool which, in some cases, calls docker build build via CLI, and it relies on the --push flag. And so far this is the only compatibility problem that I found when using podman(with podman-docker).

Additional context

I may be able to contribute a PR if you think this is not to complex, and can give me a couple of pointers in the right direction. :)