Add change log entry

Author: kimdv

Release Notes/601.md

@@ -2,6 +2,11 @@
 
 ## New APIs
 
+- `IntegerLiteralExprSyntax` now has a computed property named `representedLiteralValue` and `FloatLiteralExprSyntax` have one named `representedLiteralValue`.
+  - Description: Provides a convenience property to get the represented literval value.
+  - Issue: https://github.com/apple/swift-syntax/issues/405
+  - Pull Request: https://github.com/apple/swift-syntax/pull/2605
+
 ## API Behavior Changes
 
 ## Deprecations