docs: update changelog for v4.2.0

Author: gamemaker1

changelog.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [v4.2.0](https://github.com/express-rate-limit/rate-limit-redis/releases/tag/v4.2.0)
+
+### Added
+
+- Export `RedisStore` as a named export.
+
 ## [v4.1.2](https://github.com/express-rate-limit/rate-limit-redis/releases/tag/v4.1.2)
 
 ### Added