update CHANGELOG

Author: matthiasgeihs

packages/keyring-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add support for envelope encryption ([#5940](https://github.com/MetaMask/core/pull/5940))
+
 ### Changed
 
 - Upgrade mock encryptor to support multiple ciphertexts ([#5943](https://github.com/MetaMask/core/pull/5943))