docs: add CHANGELOG.md following Keep a Changelog format

CHANGELOG.md

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+# Changelog
+
+All notable changes to Netsleuth will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- DevContainer configuration for consistent development environment
+- Pre-commit hooks for linting, formatting, and security checks
+- Comprehensive CI/CD pipeline with GitHub Actions
+- Issue templates for bug reports and feature requests
+- Pull request template
+- CONTRIBUTING.md guide
+- Internationalization support (i18n) for multiple languages
+- Monitoring module with OpenTelemetry integration
+- Sphinx documentation structure
+- Python 3.10, 3.11, 3.12 support in CI
+
+### Changed
+- Updated pyproject.toml with comprehensive tool configurations
+- Enhanced project structure for better maintainability
+
+### Fixed
+- Improved error handling patterns
+- Better type hints throughout the codebase
+
+### Security
+- Added Bandit security scanning
+- Added pip-audit for dependency vulnerability checks
+- Automated security scanning in CI pipeline
+
+## [0.1.0] - 2024-08-12
+
+### Added
+- Initial release of Netsleuth
+- Network diagnostics capabilities
+- CLI interface
+- Multiple export formats
+- Basic testing framework
+
+[Unreleased]: https://github.com/netsleuth/netsleuth/compare/v0.1.0...HEAD
+[0.1.0]: https://github.com/netsleuth/netsleuth/releases/tag/v0.1.0