Update CHANGELOG.md

Note addition of #3265

Author: Per Larsen

CHANGELOG.md

@@ -227,6 +227,7 @@
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 # Unreleased
 ## Added
+ * Add option in CLI to use rustified repr-C enums (--rustified-repr-c-enum, #3265).
 ## Changed
 ## Removed
 - Removed support for generating code for rustc versions < 1.51.