CI: Note in the PR the versions contained in config/versions.json

[CodeGat]

In #31 I had to note that config/versions.json may need to be modified because that is the file that sources the versions of spack-config and spack-packages that are used in the deployment.

This would be annoying to do for every PR and probably also speaks to a lack of documentation on my part.

Potential Solutions

• Add a recreating comment on commit on a PR via CI noting the versions that will be used in the deployment. For example, "This spack.yaml will deploy access-om2 with spack-config 2024.01.01 and spack-packages 2024.01.01. If these are not the correct versions, modify config/versions.json"
• Add this information to the README.md or a CONTRIBUTING file.