docs: add CHANGELOG and TODO templates, update rules

CHANGELOG.package.md

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+# Changelog
+
+All notable changes to this package will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/),
+and this project adheres to [Semantic Versioning](https://semver.org/).
+
+## [Unreleased]
+
+### Added
+- Initial setup
+
+---
+
+## [0.1.0] - YYYY-MM-DD
+
+### Added
+- Feature 1
+- Feature 2
+
+### Changed
+- Change 1
+
+### Fixed
+- Bug fix 1
+
+---
+
+## Template Usage
+
+1. Replace `YYYY-MM-DD` with actual date
+2. Update sections for each release
+3. Move [Unreleased] items to new version on release
+4. Remove this section