chore: Update release changelog

Author: 96malhar

RELEASE.CHANGELOG.md

@@ -1,3 +1,10 @@
+### Release 2024-05-16
+* **Amazon.Lambda.Annotations (1.4.0)**
+  * Updated the source generator to add documentation on public members in the generated files.
+  * Added the "\<auto-generated/\>" top-level comment on the generated files to skip them from being processed by analyzers.
+  * Use the `ILambdaSerializer` to serialize the response body when returning an `IHttpResult`.
+    * BREAKING CHANGE: Removed the `JsonContext` property in the `HttpResultSerializationOptions` class and replaced it with an `ILambdaSerializer`
+
 ### Release 2024-04-25
 * **Amazon.Lambda.Annotations (1.3.1)**
   * Update User-Agent string