update CHANGELOG.md for next release

Author: fzipp

CHANGELOG.md

@@ -4,6 +4,13 @@ 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
+- Support method receivers with type parameters introduced in Go 1.18
+
+### Changed
+- Use more efficient filepath.WalkDir instead of filepath.Walk
+
 ## [0.3.1] - 2020-10-20
 ### Added
 - Test coverage