Fix testpypi publish CICD step (#3)

## Summary

Fix testpypi publish CICD step.

### Why?

Need CICD working.

### How?

- Add GH_TOKEN env variable to publish step of main Github Actions
workflow

## Checklist

Most checks are automated, but a few aren't, so make sure to go through
and tick them off, even if they don't apply. This checklist is here to
help, not deter you. Remember, "Slow is smooth, and smooth is fast".

- [X] **Unit tests**
  - Every input should have a test for it.
- Every potential raised exception should have a test ensuring it is
raised.
- [X] **Documentation**
  - New functions/classes/etc. must be added to `docs/api.rst`.
- Changed/added classes/methods/functions have appropriate
`versionadded`, `versionchanged`, or `deprecated`
[directives](http://www.sphinx-doc.org/en/stable/markup/para.html#directive-versionadded).
- The appropriate entry in `CHANGELOG.md` has been included in the
"Unreleased" section, i.e. "Added", "Changed", "Deprecated", "Removed",
"Fixed", or "Security".
- [X] **Future work**
- Future work should be documented in the contributor guide, i.e.
`.github/CONTRIBUTING.md`.

If you have any questions not answered by a quick readthrough of the
[contributor
guide](https://pysparkplug.mattefay.com/en/latest/contributor_guide.html),
add them to this PR and submit it.

.github/workflows/cicd.yaml

@@ -33,6 +33,7 @@ jobs:
         if: ${{ github.ref == 'refs/heads/main' }}
         run: ./nox.sh -s publish -- testpypi
         env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           TWINE_USERNAME: __token__
           TWINE_PASSWORD: ${{ secrets.TESTPYPI_TOKEN }}