Add CHANGELOG entry

Author: samwelkanda

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.0.0rc0] - 2023-10-27
+
+### Added
+
+### Changed
+ - Refactored request headers from dictionary to headercollection.
+
 ## [1.0.0a16] - 2023-09-19
 
 ### Added