Release v0.2.1

add codeowners (#5)

# 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.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have made corresponding changes to the documentation.
- [x] 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

- [x] Chore


## Linked tickets

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provide the ticket URL here. -->

## High level description

Add codeowners and update poetry install command in Dockerfile.

## Detailed description

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has been implemented. -->


## Describe alternatives you've considered

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considered. Be sure to explain why the existing customisability isn't
suitable for this feature. -->

## Operational impact

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the change. Is there anything in particular we should be looking at when
deploying the change to make sure it is working as intended. If
something goes wrong will any special actions be needed to revert the
change. -->

## Additional context

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here. -->