DOC: Update changelog for release of 0.4

CHANGELOG.md

@@ -5,7 +5,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased] ##
+## [0.4.0] - 2023-03-22 ##
+(Florian Spreckelsen)
 
 ### Added ###
 
@@ -41,10 +42,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   queries for identifiables since it would contain "WITH name=''" otherwise
   which is an impossible condition. If your cfoods contained this case, they are ill defined.
 
-### Security ###
-
-### Documentation ###
-
 ## [0.3.0] - 2022-01-30 ##
 (Florian Spreckelsen)