Add 5.0.0-dev16 changelog

Author: eddyashton

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [5.0.0-dev16]
+
+[5.0.0-dev16]: https://github.com/microsoft/CCF/releases/tag/ccf-5.0.0-dev16
+
+### Added
+
+- Reusable functionality for creating an in-enclave JS interpreter has been added to the public C++ API. Applications should subclass `CustomJSEndpointRegistry` to get similar behaviour to the existing JS Generic app.
+
 ## [5.0.0-dev15]
 
 [5.0.0-dev15]: https://github.com/microsoft/CCF/releases/tag/ccf-5.0.0-dev15