CI: Publish examples as Spin apps

[vdice]

The example apps in this repo are still published as stock Docker images: https://github.com/spinkube/containerd-shim-spin/blob/main/.github/workflows/docker-build-push.yaml

We should publish as Spin apps via spin registry push directly, so that they can be also be run via eg spin up -f <ref>.

One question: Do we still want to publish these examples as apps wrapped in Docker image form? Or would we like to fully switch to publishing solely via spin registry push? Yes, as answered below, we need to keep publishing as Docker images.

[mikkelhegn]

Last I tried, I believe Docker Desktop and Rancher does not support that format, but only the Docker images format at this point.

[Mossaka]

+1 to @mikkelhegn comment. However, I'd like to publish the images to the standardized format when Docker Desktop and Rancher support them.

[vdice]

Thank you @mikkelhegn and @Mossaka. Ok, for now, we should publish the examples as Spin apps in addition to their current Docker image forms.

Next question: naming. The current Docker image references have names like ghcr.io/spinkube/containerd-shim-spin/examples/spin-rust-hello:v0.15.1. Shall we publish as Spin apps to references such as ghcr.io/spinkube/containerd-shim-spin/examples/apps/spin-rust-hello:v0.15.1? Open to suggestions!

[Mossaka]

yeah I like the addition of category names to images. 👍 for me