chore: update outdated Contributing guide to reflect CHANGELOG check

Author: EchoEllet

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,8 @@
 <!-- 
 Briefly describe your changes and summarize in the title.
 Contributor Guide: https://github.com/singerdmx/flutter-quill/blob/master/CONTRIBUTING.md
-Package versioning is automated; add updates to `Unreleased` per [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format.
+Package versioning is automated.
+Add updates to `Unreleased` in `CHANGELOG.md` following [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format.
 -->
 
 ## Description

CONTRIBUTING.md

@@ -10,8 +10,8 @@ First, we would like to thank you for your time and efforts on this project, we
 > explaining your proposed changes and their rationale for a higher chance of acceptance. Thank you!
 
 > [!NOTE]
-> Updating the `CHANGELOG.md` is optional. If updated, follow the [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format in the `Unreleased` section.  
-The package version in `pubspec.yaml` should not be modified; this will be handled by a maintainer or CI.
+> The package version in `pubspec.yaml` **should not be modified**; this will be handled by a maintainer or CI.
+> Add updates to `Unreleased` in `CHANGELOG.md` following [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format.
 
 ## 📋 Development Prerequisites