[ci skip] Update CHANGELOG.md

Author: yhatt

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Define the default 16:9 size preset to built-in themes ([#250](https://github.com/marp-team/marp-core/pull/250))
 
+### Changed
+
+- Upgrade dependent packages to the latest version ([#253](https://github.com/marp-team/marp-core/pull/253))
+
 ## v2.1.0 - 2021-07-19
 
 ### Added