GitHub Packages changes

[thomas-bc]

2 changes:

1. Added a label to the image. See https://docs.github.com/en/enterprise-server@3.8/packages/working-with-a-github-packages-registry/working-with-the-container-registry#labelling-container-images. This is to have it show up in the homepage of the repository, under Packages etc... (I believe)
2. Changed the way CI authenticates to ghcr.io registry, as suggested by https://docs.github.com/en/actions/security-guides/automatic-token-authentication

[thomas-bc]

I manually canceled the push event so as not to build the same image twice. We may want to restrict the events that actually build the image since it's a fairly large one.
Other than that, things look good! https://github.com/fprime-community/fprime-workspace-image/pkgs/container/fprime-workspace-image

docker pull ghcr.io/fprime-community/fprime-workspace-image:pr-49 looks quite neat

[capsulecorplab]

Cool! I've been wondering how to get the image to show up under Packages on the repo homepage, glad you figured that out!

[capsulecorplab]

Just pulled and ran ghcr.io/fprime-community/fprime-workspace-image:pr-49!

[capsulecorplab]

LGTM!

[capsulecorplab]

Also, opened #50 to disable redundant builds