docs: format changelog

Author: Yukaii

CHANGELOG.md

@@ -1,13 +1,20 @@
 # Changelog
+
 All notable changes to HackMD-CLI will be documented in this file.
 
-## [Unreleased]
+## 2.0.0
+
 ### 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
+- CodiMD has not been supported