Podman support #226

Description
Also supporting Podman

Alternatives considered
Can only have Podman on the concerned host.

Additional context
Tried to use it with podman-docker (which creates a docker script that runs podman, and also links /var/run/docker.sock to /run/podman/podman.sock.

The problem is that the output of the commands (e.g. docker system ps --format "{{json .}}" or docker events --format "{{json .}}") are not exactly the same. Maybe by having structs to also parse Podman outputs, Docuum could also work for Podman.