feat: support nerdctl engine

[darktohka]

Right now, there is no support for nerdctl, a pretty nifty container CLI for containerd: https://github.com/containerd/nerdctl

This PR adds support for a new image source: nerdctl

This image source is supported on all OSes, nerdctl has support for Linux, Windows and Darwin as well.

Nerdctl saves images using nerdctl image save <id>. If this errors (the image may not exist), nerdctl pull <id> is tried to pull the image if possible.

Nerdctl can also build images the same way as the Docker CLI (nerdctl build --iidfile)

[joschi]

@darktohka Thanks a lot for your contribution!

Do you think you could add an integration test for this functionality?

Maybe looking into how kind is doing it for nerdctl and Podman might help:

• https://github.com/kubernetes-sigs/kind/blob/v0.27.0-alpha/.github/workflows/nerdctl.yaml#L37-L50
• https://github.com/kubernetes-sigs/kind/blob/v0.27.0-alpha/.github/workflows/podman.yml#L37-L48

[joschi]

@darktohka With https://github.com/wagoodman/dive being maintained again, you might want to open a pull request there to add support for nerdctl in the upstream project.