Support podman

[awoimbee]

Is your feature request related to a problem? Please describe.

While docker still has momentum, Podman is rapidly replacing it. I am personally forced to use it to avoid ugly hacks in my container builds.
Problem: I can't login to ECR, via OIDC (see), without installing aws-cli.

Describe the solution you'd like
Github's ubuntu runners apparently have podman bundled. It would be nice if this action automatically detected if podman, docker or both are installed and would configure both automagically.

Describe alternatives you've considered
Use aws-cli:

	aws --profile foo ecr get-login-password --region eu-east-1 | tee \
		>(docker login --username AWS --password-stdin $ECR_URI)\
		>(podman login --username AWS --password-stdin $ECR_URI)\
		>/dev/null | cat || true

Keywords: podman, buildah