docs: recommend custom environment prefix - #1063

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: hkusu/review-assign-action@5bee595fdb9765d4a0bd35724b6302fa15569158. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/