Add changelog entry

docs/changelog.md

@@ -8,6 +8,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). See the [Contributing Guide](contributing.md) for details.
 
+## [Unreleased]
+
+### Fixed
+
+* Improve and expand type annotations in the codebase (#1394)
+
 ## [3.5] -- 2023-10-06
 
 ### Added