Update CHANGES.md

CHANGES.md

@@ -21,7 +21,8 @@ Core Grammars:
 - fix(typescript) - Fixedoptional property not highlighted correctly  [Dxuian]
 - fix(ruby) - fix `|=` operator false positives (as block arguments) [Aboobacker MK]
 - fix(sql) - Fixed sql primary key and foreign key spacing issue   [Dxuian]
-
+- fix(cpp) added flat_set and flat_map as a part of cpp 23 version [Lavan]
+
 New Grammars:
 
 - added 3rd party TTCN-3 grammar to SUPPORTED_LANGUAGES [Osmocom][]
@@ -53,6 +54,7 @@ CONTRIBUTORS
 [Sainan]: https://github.com/Sainan
 [Osmocom]: https://github.com/osmocom
 [Álvaro Mondéjar]: https://github.com/mondeja
+[Lavan]: https://github.com/jvlavan
 
 
 ## Version 11.10.0