Build container image in two steps (new action)

[gvegayon]

This pull request introduces a new workflow for building and pushing container images in two steps, along with relevant documentation and examples. The most important changes include the addition of a new workflow file, updates to the action configuration, and new example files.

New workflow and action configuration:

• Added test-twostep-container-build.yml to define a new workflow for building and pushing container images in two steps.
• Created twostep-container-build/action.yml to configure the new action with necessary inputs and steps.

Documentation and examples:

• Updated twostep-container-build/README.md with detailed instructions and examples for using the new two-step container build action.
• Added example container files twostep-container-build/examples/Containerfile and twostep-container-build/examples/Containerfile.dependencies to demonstrate the two-step build process. [1] [2]
• Added twostep-container-build/examples/example.yaml as a sample workflow configuration for using the new action.

Minor changes:

• Removed pull_request_target trigger from .github/workflows/test-post-artifact.yml.

[github-actions]

Thank you for your contribution @damonbayer 🚀! Your readme-ubuntu-latest is ready for download 👉 here 👈!
_{(The artifact expires on 2025-03-02T16:20:07Z. You can re-generate it by re-running the workflow here.)}

[github-actions]

Thank you for your contribution @damonbayer 🚀! Your readme-macos-latest is ready for download 👉 here 👈!
_{(The artifact expires on 2025-03-02T16:20:07Z. You can re-generate it by re-running the workflow here.)}

[github-actions]

Thank you for your contribution @damonbayer 🚀! Your readme-windows-latest is ready for download 👉 here 👈!
_{(The artifact expires on 2025-03-02T16:20:07Z. You can re-generate it by re-running the workflow here.)}

[github-actions]

Thank you for your contribution @damonbayer 🚀! Your readme-rocker is ready for download 👉 here 👈!
_{(The artifact expires on 2025-03-02T16:20:07Z. You can re-generate it by re-running the workflow here.)}

[gvegayon]

Hey @dylanhmorris, I've tagged you as a reviewer for this PR, but don't feel pressured! I'll see if we have someone else who could help with it (another maintainer for the cfa-actions project).

[gvegayon]

Hey @damonbayer! Could you take a look into this PR? This is relevant for pyrenew-hew, so it'd be great if we could merge this to update the workflow there.

[damonbayer]

@gvegayon I fixed a broken link. Otherwise, looks good to me! Thanks!

[gvegayon]

Thank you, @damonbayer! I'll create a PR to pyrenew-hew using this approach instead.

attn @zsusswein and @micahwiesner67. I'll do the same for the epinow2-pipeline and respnet-nowcasting repos.