Add change log

Author: James Tsai

CHANGELOG.md

@@ -0,0 +1,13 @@
+# Changelog
+All notable changes to HackMD-CLI will be documented in this file.
+
+## [Unreleased]
+### Added
+- Rewrite old and add new commands supported by [v2 @hackmd/api](https://www.npmjs.com/package/@hackmd/api)
+- Github Action CI for config testing
+### Changed
+- Migrate [oclif](https://www.npmjs.com/package/oclif) to v2.5.0
+- Change to use hackmd api end point URL and and access token for authentication
+### Removed
+- Remove commands based on deprecated v1 @hackmd/api, including `import`, `export`
+- CodiMD has not been supported