Releasing a new version

1. Merge all code into main
2. Run the "Create release" workflow (https://github.com/nationalarchives/ds-wagtail/actions/workflows/create-release-tag.yml) against the main branch
3. A pull request is created with the release number in calver format
4. A release is drafted
5. A tag is created
6. Merge the created pull request into main to update the release number
7. Publish the drafted release that was created on the releases page
8. A Docker image will be created
9. The site will be pushed to platform.sh
10. Pull the changes from main down to develop