docs: add CHANGELOG.md for v0.2.0 release

Document all changes since v0.1.0 including:
- New features: contig depths, study downloads, disk caching
- Improved type hints and code quality
- Bug fixes for URLs and metadata handling
- Extensive documentation improvements
- Enhanced test coverage

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: areias03

CHANGELOG.md

@@ -0,0 +1,80 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [0.2.0] - 2026-03-23
+
+### Added
+- Full download functionality for study data ([e6d9fe9](https://github.com/areias03/SPIREpy/commit/e6d9fe9))
+- Sample contig depths feature ([a972e4f](https://github.com/areias03/SPIREpy/commit/a972e4f))
+- Disk caching for cluster and genome metadata ([700d693](https://github.com/areias03/SPIREpy/commit/700d693))
+- Comprehensive unit and integration tests for data functions ([b61a145](https://github.com/areias03/SPIREpy/commit/b61a145))
+- Docstring and type hint for `get_contig_depths()` method ([0603ef6](https://github.com/areias03/SPIREpy/commit/0603ef6))
+
+### Changed
+- Improved type hints: updated return type annotations to use `pl.DataFrame` instead of `pl.dataframe.DataFrame` ([072f10b](https://github.com/areias03/SPIREpy/commit/072f10b))
+- Added `Union` type hint for `get_amr_annotations()` to properly handle `None` return ([072f10b](https://github.com/areias03/SPIREpy/commit/072f10b))
+- Use more Polars-style code patterns ([35e460d](https://github.com/areias03/SPIREpy/commit/35e460d))
+- Use "SPIREpy" as logger name ([5ec51a7](https://github.com/areias03/SPIREpy/commit/5ec51a7))
+- Only import pandas when needed to improve performance ([4b9fc13](https://github.com/areias03/SPIREpy/commit/4b9fc13))
+- Improved code formatting and consistency in test files ([072f10b](https://github.com/areias03/SPIREpy/commit/072f10b))
+
+### Fixed
+- Sample and study metadata URL handling ([c73b09d](https://github.com/areias03/SPIREpy/commit/c73b09d))
+- Unit testing calls and expected URL ([d3e7ec3](https://github.com/areias03/SPIREpy/commit/d3e7ec3))
+- Adapted unit tests to new function signatures ([e9e9e8c](https://github.com/areias03/SPIREpy/commit/e9e9e8c))
+- `sample.get_mags()` now correctly reads genome metadata ([eaec357](https://github.com/areias03/SPIREpy/commit/eaec357))
+- Import error resolution ([0e71aa4](https://github.com/areias03/SPIREpy/commit/0e71aa4))
+- Double calls on methods ([febefaf](https://github.com/areias03/SPIREpy/commit/febefaf))
+
+### Removed
+- Multithreading utilities ([e06f92a](https://github.com/areias03/SPIREpy/commit/e06f92a))
+- Unnecessary comments in view.py ([072f10b](https://github.com/areias03/SPIREpy/commit/072f10b))
+
+### Documentation
+- Added comprehensive docstring for `get_contig_depths()` method ([0603ef6](https://github.com/areias03/SPIREpy/commit/0603ef6))
+- Added function docstrings for better code documentation ([2f682f4](https://github.com/areias03/SPIREpy/commit/2f682f4))
+- Better docstrings throughout the codebase ([6e4d027](https://github.com/areias03/SPIREpy/commit/6e4d027))
+- Major improvements to documentation ([4424408](https://github.com/areias03/SPIREpy/commit/4424408))
+- Fixes to Sphinx documentation generation ([b8f2314](https://github.com/areias03/SPIREpy/commit/b8f2314))
+- Improvements to ReadTheDocs configuration ([afb917e](https://github.com/areias03/SPIREpy/commit/afb917e))
+- Formatting improvements for Sphinx docstrings ([e25d7b7](https://github.com/areias03/SPIREpy/commit/e25d7b7))
+- Added reference to Sample class ([77b684b](https://github.com/areias03/SPIREpy/commit/77b684b))
+- Added citation to README with syntax fixes ([567c92e](https://github.com/areias03/SPIREpy/commit/567c92e))
+- Improvements to README.md ([dac542a](https://github.com/areias03/SPIREpy/commit/dac542a))
+- Added badges to README.md ([15ac08b](https://github.com/areias03/SPIREpy/commit/15ac08b))
+
+### Testing
+- Better unit and integration tests ([8d22854](https://github.com/areias03/SPIREpy/commit/8d22854))
+
+## [0.1.0] - 2025-06-24
+
+### Added
+- Initial release of SPIREpy
+- SPIRE wrapper and command-line tool for interacting with global microbiome data
+- Study class for managing study-level data
+- Sample class for managing sample-level data
+- Genome class for managing genome-level data
+- CLI interface with `spire` command
+- Support for downloading MAGs (Metagenome-Assembled Genomes)
+- AMR (Antimicrobial Resistance) annotations support
+- Disk caching for large SPIRE data
+- Comprehensive documentation with Sphinx
+- Unit and integration tests with pytest
+- Support for Python 3.9, 3.10, 3.11, 3.12, and 3.13
+
+### Dependencies
+- polars
+- pandas
+- rich
+- joblib
+- platformdirs
+
+[Unreleased]: https://github.com/areias03/SPIREpy/compare/v0.2.0...HEAD
+[0.2.0]: https://github.com/areias03/SPIREpy/compare/v0.1.0...v0.2.0
+[0.1.0]: https://github.com/areias03/SPIREpy/releases/tag/v0.1.0