New release checklist BG standard: `python -m build` and `twine check dist/*`

Please use the latest `release_checklist.md` containing `python -m build` and `twine check dist/*` https://github.com/Billingegroup/cookiecutter/blob/main/%7B%7B%20cookiecutter.repo_name%20%7D%7D/.github/ISSUE_TEMPLATE/release_checklist.md