Adding dockerhub release method

[dblane-digicatapult]

Pull Request

Checklist

• Have you read Digital Catapult's Code of Conduct?
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.

PR Type

Please delete options that are irrelevant.

• Chore

Linked tickets

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High level description

Adds Dockerhub Release mechanism

Detailed description

Adding dockerhub release method so we can push containers to both GHCR and dockerhub so people can use containers without requiring authentication to GHCR.

Describe alternatives you've considered

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Operational impact

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Additional context

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