Document release branch workflow

doc/maintainers/release.md

@@ -3,6 +3,10 @@
 This project uses simple tags, that trigger a release of all crates using Hercules CI.
 See [HCI Effects cargo publish workflow].
 
+## Release branch
+
+Create a `release` branch and PR for release preparation. This allows CI to validate the release before tagging.
+
 ## Before tagging
 
 - Update `CHANGELOG.md`:
@@ -12,6 +16,9 @@ See [HCI Effects cargo publish workflow].
 ## After tagging
 
 - Add a new Unreleased section to `CHANGELOG.md`
+- Merge the release PR
+
+---
 
 Dissatisfied with the coarse grained release process? Complain to @roberth and he'll get it done for you.