Add container image

[TristanCacqueray]

This change enables running emanote in a container.

[TristanCacqueray]

Note that I haven't tested the CI action, but that's the script I'm using elsewhere and I hope it will work as-is.

[TristanCacqueray]

That's odd, the script works with the default action runner, here is an example: https://github.com/logjuicer/logjuicer/actions/runs/10422103187/job/28865852855

I guess the XDG_RUNTIME_DIR of your runner is not writable, perhaps try setting it to a valid location for this task?

[srid]

XDG_RUNTIME_DIR

Curious this is a requirement of skopeo? If so crane may be worth looking into, as we've got it working with the same kind of runners: https://github.com/nammayatri/nammayatri/blob/acced803e46a801edada92cd1fd5fa769790deb2/.github/workflows/nix.yaml#L113-L127

As a stretch goal only, it'd be good to use https://github.com/nlewo/nix2container over pkgs.dockerTools.

[TristanCacqueray]

@srid I think skopeo/podman writes the credentials to /run .

Also, once the package is created on GH you'll have to mark at as public so that it can be used freely.

[srid]

@TristanCacqueray

I got the image push working by switching to crane. I had to re-open this PR because forks can't push images, it seems. Let's move this discussion to #586