ci: add GitHub CI

[JeronimoMendes]

This PR adds the following:

• Linting job (runs flake8 and black with auto fix)
• Unit test job
• Conventional commit checker job
• Pre-commit hooks
• Automatically update CHANGELOG on PR
• Create new release tag on merge onto master
• Build and upload docker image to registry on new tag

Let me know if you remember any useful jobs to be added

Closes #1

[codecov-commenter]

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