Add changelog entry

Author: zoewangg

.changes/next-release/feature-AmazonS3-c101d4d.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "Amazon S3",
+    "contributor": "",
+    "description": "S3 client behavior is updated to always calculate a checksum by default for operations that support it (such as PutObject or UploadPart), or require it (such as DeleteObjects). The checksum algorithm used by default is CRC32. The S3 client attempts to validate response checksums for all S3 API operations that support checksums. However, if the SDK has not implemented the specified checksum algorithm then this validation is skipped. See [Dev Guide](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/s3-checksums.html) for more information"
+}