Add changelog (#6454)

Author: dagnir

.changes/next-release/feature-AWSSDKforJavav2-9d16701.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "This update enables reusing the initially computed payload checksum of a request across all request attempts. This ensures that even if the content is changed from one attempt to the next, the checksum included in the request will remain the same and the request will be rejected by the service."
+}