[doc] create CHANGELOG

src/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).
+
+## [Unreleased]
+
+### Added
+
+- Read/write DEWIF file content #1
+- Aes256 encryption/decryption
+- hashs::Hash impl AsRef<[u8]>
+
+### Changed
+
+- Ed25519KeyPair::generate_signator cannot fail.
+
+### Security
+
+- Ed25519KeyPair must not expose seed
+
+## [0.8.0] - 2020-01-16
+
+Initial version.