Update CHANGELOG.md

Author: devinroth

CHANGELOG.md

@@ -13,11 +13,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Create multi-output / aggregate device with installer.
 - Keep track of which apps are connected to the driver.
 
-## [0.4.0] - Unreleased
+## [0.4.0] - 2021-06-10
 ### Added
 - Hidden duplicate device.
 - Ability to easily modify device streams. 
 - Builds multiple versions.
+- create_installer.sh to easily build multiple channel versions. 
 
 ### Changed
 - Fix potential memory leak.