Publish Docker image for linux/arm64 platform

[keynmol]

We already have an external Docker build, but we might need to change things around labelling.

After that, the story around cross-publishing is well documented.

I believe this entire block is copypastable with minimal adjustments: https://github.com/indoorvivants/sn-vcpkg/blob/main/.github/workflows/ci.yml#L163-L256