docs: prepare changelog for release (#19)

Author: loozhengyuan

CHANGELOG.md

@@ -2,9 +2,9 @@
 
 All notable changes to this project will be documented in this file.
 
-## [Unreleased]
+## [v0.2.0] - 2021-02-24
 
-<!-- START Unreleased -->
+<!-- START v0.2.0 -->
 
 ### Added
 
@@ -18,7 +18,7 @@ All notable changes to this project will be documented in this file.
 
 * Set go.mod `go` directive to minimum supported Go version ([#12](https://github.com/loozhengyuan/grench/pull/12))
 
-<!-- END Unreleased -->
+<!-- END v0.2.0 -->
 
 ## [v0.1.0] - 2021-02-17
 
@@ -28,5 +28,5 @@ Initial release.
 
 <!-- END v0.1.0 -->
 
-[Unreleased]: https://github.com/loozhengyuan/grench/compare/v0.1.0...HEAD
+[v0.2.0]: https://github.com/loozhengyuan/grench/releases/tag/v0.2.0
 [v0.1.0]: https://github.com/loozhengyuan/grench/releases/tag/v0.1.0