docs: document protected branch release flow - #11

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/dependency-review-action@40c09b7dc99638e5ddb0bfd91c1673effc064d8a. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/