Update changelog section from 'Unreleased' to 'Released'

Author: namanONcode

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to zThread 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).
 
-## [Unreleased]
+## [Released]
 
 ### Added
 - Core event runtime API with `ZRuntime`, `EventLoop`, `EventDispatcher`, and `Scheduler`