DOC: update CHANGELOG

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* New version history feature. The "H" container flag retrieves the full
+  version history during a transaction (e.g. during Retrievals) and constructs
+  a tree of successors and predecessors of the requested entity version.
 * New query functionality: `ANY VERSION OF` modifier. E.g. `FIND ANY VERSION OF
   RECORD WITH pname=val` returns all current and old versions of records where
   `pname=val`. For further information, examples and limitations see the wiki