Mention fair nesting operations in the changelog

Author: harendra-kumar

core/docs/Changelog.md

@@ -9,6 +9,9 @@ full list of deprecations, additions, and changes to the function signatures.
 
 * Added APIs for prompt cleanup of resources, allowing guaranteed
   cleanup as an alternative to GC-based cleanup.
+* Added operations for fair nesting of inner and outer streams for
+  exploring them equally, generally useful but especially useful for logic
+  programming use cases.
 * Introduced `Streamly.Data.Scanl` with a new `Scanl` type. Scans can
   split a stream into multiple streams, process them independently, and
   merge the results. The `Fold` type is now split into `Fold` and `Scanl`.