chore: add canonical references to CHANGELOG

CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Introduce canonical reference rules via a payload entry in the identity
+  document. The payload is identified by `xyz.radicle.crefs`, and the payload
+  currently contains one key `rules`, which is followed by the set of rules. For
+  each rule, there is a reference pattern string to identify the rule, which in
+  turn is composed of the `allow` and `threshold` values. The canonical
+  reference rules are now used to check for canonical updates. The rule for the
+  `defaultBranch` of an `xyz.radicle.project` is synthesized from the identity
+  document fields: `threshold` and `delegates`. This means that a rule for that
+  reference is not allowed within the rule set. This checked when performing a
+  `rad id update`.
+
 ## Release Highlights
 
 ## Deprecations