docs: update changelog

Author: glennsl

Diff for: CHANGELOG.md

@@ -11,6 +11,7 @@
 - Add `Array.at` binding for returning an array item by its index. https://github.com/rescript-association/rescript-core/pull/48
 - Fixed type signatures of `Array.fromArrayLikeWithMap` and `Array.fromIteratorWithMap`. https://github.com/rescript-association/rescript-core/pull/50
 - Remove internal async/await helpers that do not need to be exposed in `Core`.
+- Add `some`, `flat`, `expect`, `zip` and `or` to `Option`, deprecate `orElse`.
 
 ### Documentation