Consider using "reusable workflows"

[BYK]

GitHub Actions now supports "reusable workflows" inside an organization: https://docs.github.com/en/actions/using-workflows/reusing-workflows#passing-inputs-and-secrets-to-a-reusable-workflow

Looks like we can replace the "setup a workflow that uses action-prepare-release" part in the readme with a simpler thing, with secrets: inherit to reduce potential for errors.

cc @chadwhitacre

[BYK]

This is done with getsentry/craft#667