Update CHANGELOG.md

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project are documented in this file.
 
 *Note:* the project underwent a maintenance shift in the creation of v0.4.0.
 
+## Head
+
+### Changes
+
+- Added: docs load mermaid.js by default by @mattxwang in https://github.com/just-the-docs/just-the-docs/pull/935
+
 ## v0.4.0.rc1
 
 ### We're back!