add changelog

Author: cometkim

CHANGELOG.md

@@ -23,6 +23,7 @@
   - Removed empty line at the end of `switch` statement
   - Removed empty `default` case from `switch` statement in the generated code
 - Optimised the Type Extension runtime code and removed trailing `/1` from `RE_EXN_ID` https://github.com/rescript-lang/rescript-compiler/pull/6958
+- Compact output for anonymous functions. https://github.com/rescript-lang/rescript-compiler/pull/6945
 
 #### :bug: Bug Fix
 - Fix issue where long layout break added a trailing comma in partial application `...`. https://github.com/rescript-lang/rescript-compiler/pull/6949