changelog update

Author: ZeeCoder

CHANGELOG.md

@@ -5,8 +5,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [3.1.0]
+
+### Added
+
+- `postcss-container-query`
+  - Allowing for one `@define-container;` declaration to override the container
+    selector detected automatically in singleContainer mode
+
 ## [3.0.1]
 
+### Changed
+
 - readme updates
 
 ## [3.0.0]