Consider adding a changelog to track version history

## Feature Request

### Summary
A `CHANGELOG.md` file would help users understand what changed between versions and make upgrade decisions easier.

### Motivation
When upgrading dependencies, developers need to know:
- What bugs were fixed
- What new features were added
- Whether there are any breaking changes

### Suggested Format
Follow the [Keep a Changelog](https://keepachangelog.com) convention:

```markdown
# Changelog

## [Unreleased]

## [1.2.0] - 2024-01-15
### Added
- New feature X
### Fixed
- Bug with Y under Z conditions
### Changed
- Behaviour of Z is now more consistent
```

### Additional Context
This is purely a documentation change with no code impact.

Start by reviewing the Keep a Changelog convention linked in the issue and the repository's existing version history. Create CHANGELOG.md with the proposed sections and record the relevant releases, changes, fixes, features, and breaking changes; done when users can use it to compare versions and assess upgrades.

Written by the indexing model from the issue text.