Added a pipeline to buid container and push to ghcr.io

[Izzy-Irvine]

I've created a pipeline that builds the container image and and pushes it to ghcr.io whenever a new release is created. I've created this to make it easier for me to self host this app although I'm sure it could help many others too.

The pipeline has been tested here: https://github.com/Izzy-Irvine/spliit/actions/runs/14594511296

Note to the maintainer:
After this PR has been merged and the first release is created, please double check that the package visibility it set to public so anybody can pull it.
https://github.com/orgs/spliit-app/packages/container/spliit/settings (link will only work after the pipeline has been run)

[Izzy-Irvine]

If you're okay with me doing so, I intend to create a PR for a Helm chart, Kustomization base or just some example manifests for deploying this into k8s. But this PR is a prerequisite for that.

[gravelfreeman]

I would like to use this. Looking forward to it.

[pm-melo]

This would be awesome. Looking forward to it.

[Petersmit27]

Tried this in my own fork and LGTM! Thanks for this :)

[Petersmit27]

I don't have the permissions to push an image to the registry yet, but I'll do this for the latest version as soon as I get permissions :)

[sevfyi]

I don't have the permissions to push an image to the registry yet, but I'll do this for the latest version as soon as I get permissions :)

looking forward to it! thanks for putting in the effort!

[Sunsurfer89]

I don't have the permissions to push an image to the registry yet, but I'll do this for the latest version as soon as I get permissions :)

Have you been successful already?
I'm really looking forward to it! This feature is much appreciated 👏 many thanks in advance! 👍

[Petersmit27]

It public now! https://github.com/spliit-app/spliit/pkgs/container/spliit