Add compatility with podman

[katsuya-horiuchi]

I use podman and having compatibility with it would be great.
Briefly I checked out the code and replacing hard-coded docker command worked for me.

There's a brief discussion on this in #113.
While the podman documentation says you can make an alias for podman, neovim doesn't seem to load alias in the first place.
So something like this would be nice:

require("netman").setup({ docker_cmd = "podman" })

[apple1417]

I'll also request being able to use an array of args. In my case I installed some podman-docker package, so the alias does work, and the plugin works perfectly fine. However, it turns out podman doesn't doesn't share containers between root/non-root, sudo podman ps returns different containers to podman ps. It would be nice if I could do something like this for projects which require root:

require("netman").setup({ docker_cmd = { "sudo", "podman" } })

[miversen33]

Sudo is going to be something that I can't guarantee will work (because netman has no way of getting your password for it).

That said, I like this general idea so it's definitely something that should be added. Dunno when I'll get around to it but I do like it