Add changelog entry

Author: rvs314

CHANGELOG.md

@@ -42,6 +42,9 @@ Minor improvements
 * Moved the concept `Irrelevant` of irrelevance (h-proposition) from `Relation.Nullary`
   to its own dedicated module `Relation.Nullary.Irrelevant`.
 
+* Provided the existing implementation of `IsString (List Char)` from
+  `Data.List.Literals` as an instance in `Data.List.Instances`.
+
 Deprecated modules
 ------------------