Create CHANGELOG.md

CHANGELOG.md

+# 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).
+
+## [0.3.0] - 2022-07-08
+### Added
+- Added `flip` command, for flipping an image along one or both axes.
+- Added `rotate` command to apply a rotation to an image, in steps of 90 degrees.
+
+## [0.2.0]
+### Added
+- Added `pipeline` command, for applying a series of transformations to an image.
\ No newline at end of file