Adding back the id on push to dockerhub action

[pacostas]

Summary

On this step https://github.com/paketo-buildpacks/github-config/blob/ed11d20621aa11f7fbf6c2c29dbd3bcc7efebb56/implementation/.github/workflows/push-buildpackage.yml#L100 the image and digest are being used from the previous step. Due to previous step does not have an id, the value of both variables is empty.

This PR adds back the id on the push to dockerhub step

Use Cases

Checklist

• [x] I have viewed, signed, and submitted the Contributor License Agreement.
• [ ] I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• [x] I have added an integration test, if necessary.
• [x] I have reviewed the styleguide for guidance on my code quality.
• [x] I'm happy with the commit history on this PR (I have rebased/squashed as needed).