chore: Add initial changelog file following Keep a Changelog format

Author: ViratiAkiraNandhanReddy

CHANGELOG.md

@@ -0,0 +1,48 @@
+# 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/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+-
+
+### Changed
+-
+
+### Deprecated
+-
+
+### Removed
+-
+
+### Fixed
+-
+
+### Security
+-
+
+## [1.0.0] - 2026-05-16
+
+### Added
+- Core Caesar cipher encryption and decryption functionality
+- Customizable shift parameter for encryption/decryption
+- Support for altering digits (`alterNumbers` / `isNumbersAltered` flags)
+- Support for altering symbols (`alterSymbols` / `isSymbolsAltered` flags)
+- File-based encryption via `encrypt_file()` method
+- File-based decryption via `decrypt_file()` method
+- Input validation for text, shift values, and file operations
+- Intuitive API with `Encryption` and `Decryption` classes
+- Basic emoji support for encryption and decryption
+- Support for both uppercase and lowercase letters
+- Comprehensive unit tests for encryption and decryption functionality
+- File I/O tests for encrypt/decrypt file operations
+- PyPI package distribution
+- GitHub Actions CI/CD pipeline for automated testing
+- Comprehensive documentation and usage examples
+
+[unreleased]: https://github.com/ViratiAkiraNandhanReddy/CaesarCipher.extended-python.pypi/compare/v1.0.0...HEAD
+[1.0.0]: https://github.com/ViratiAkiraNandhanReddy/CaesarCipher.extended-python.pypi/releases/tag/v1.0.0