Update CHANGELOG.md

Author: MKodde

CHANGELOG.md

@@ -5,6 +5,18 @@ We will continue to post relevant release notes on the GitHub release page. More
 
 More information about our release strategy can be found in the [Development Guidelines](https://github.com/OpenConext/OpenConext-engineblock/wiki/Development-Guidelines#release-notes) on the EngineBlock wiki.
 
+## 6.3.6
+After some testing, @tvdijen opened issue #920, identifying several issues with the 3.6.x releases. Those issues
+have been addressed in this release.
+
+**Bugfixes**
+* Allow responses without NameID #919
+* Add c14n method to the reference transforms in XML metadata. #921
+* Prevent undefined access in Assembler #923
+
+**Chore**
+* Remove the remaining eduGAIN metada fields #922
+
 ## 6.3.5
 **Bugfix**
  - Clean up unused usage of AuthnRequest destination #898