[DynamoDb] Prepare for 0.3.1 (#696)

* [DynamoDb] Prepare for 0.3.1

* Update src/Service/DynamoDb/CHANGELOG.md

Co-authored-by: Jérémy Derussé <jeremy@derusse.com>

Co-authored-by: Jérémy Derussé <jeremy@derusse.com>

Author: Nyholm

CHANGELOG.md

@@ -2,6 +2,17 @@
 
 ## NOT RELEASED
 
+## 0.3.1
+
+### Added
+
+- Added operation `BatchWriteItem`
+- Added operation `BatchGetItem`
+
+### Fixed
+
+- Internally we make a difference between null and an empty array
+
 ## 0.3.0
 
 ### Added