Add missing unreleased reference in changelogs (#53)

Author: Mrtenz

packages/codeql-action/CHANGELOG.md

@@ -12,3 +12,5 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Migrated action from its separate repository to the monorepo
 - Added multi language support
 - Updated CodeQL action to v4
+
+[Unreleased]: https://github.com/metamask/action-security-code-scanner/

packages/language-detector/CHANGELOG.md

@@ -10,3 +10,5 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Added support for autodetecting languages using Github API
+
+[Unreleased]: https://github.com/metamask/action-security-code-scanner/

packages/semgrep-action/CHANGELOG.md

@@ -10,3 +10,5 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Migrated action from its separate repository to the monorepo
+
+[Unreleased]: https://github.com/metamask/action-security-code-scanner/