Update CHANGELOG.md

Author: maxep

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+# 3.5.1 / 23-01-2025
+
+- [FIX] Fix crash in App Hangs backtrace generation. See [#2647][]
+
 # 3.5.0 / 12-01-2025
 
 - [FEATURE] Report time to initial display (TTID). See [#2517][] [#2464][] 
@@ -1019,6 +1023,7 @@ Release `2.0` introduces breaking changes. Follow the [Migration Guide](MIGRATIO
 [#2614]: https://github.com/DataDog/dd-sdk-ios/pull/2614
 [#2631]: https://github.com/DataDog/dd-sdk-ios/pull/2631
 [#2633]: https://github.com/DataDog/dd-sdk-ios/pull/2633
+[#2647]: https://github.com/DataDog/dd-sdk-ios/pull/2647
 
 [@00fa9a]: https://github.com/00FA9A
 [@britton-earnin]: https://github.com/Britton-Earnin