Add #657 to CHANGELOG

Author: pluma

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 
 - Added `uuid` and `padded` to legal `KeyGeneratorType` values in TypeScript ([#656](https://github.com/arangodb/arangojs/issues/656))
+- Added `overwrite` to `InsertOptions` type in TypeScript ([#657](https://github.com/arangodb/arangojs/issues/657))
 
 ## [6.14.0] - 2020-03-18