Update changelog

Author: isc-pbarton

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Changing system mode (environment name) in setting spersists after instance restart (#655)
 - Popping from stash is more responsive (#687)
 - Favorites links for Git pages now works on recent IRIS versions (#734)
+- IDE editing of decomposed productions now properly handles adds and deletes (#643)
 
 ### Fixed
 - Fixed error running Import All when Git settings file does not exist (#713)