Release v0.2.0

Adding dockerhub release method (#4)

# Pull Request

## Checklist
- [X] Have you read Digital Catapult's [Code of
Conduct](https://github.com/digicatapult/.github/blob/main/CODE_OF_CONDUCT.md)?
- [X] I have performed a self-review of my own code.
- [X] I have commented my code, particularly in hard-to-understand
areas.
- [X] 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.

- [X] Chore

## Linked tickets

N/A

## 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

N/A
## Operational impact

N/A
## Additional context

N/A