feat: release optional promotin source type in order (#38)

BREAKING CHANGE: release optional promotion source type in order

Author: ellanan

README.md

@@ -350,4 +350,4 @@ You can learn more about the Rollup API and configuration [here](https://github.
 ## Terms And Conditions
 
 - Any changes to this project must be reviewed and approved by the repository owner.
-- For more information about the license, see [MIT License](https://github.com/elasticpath/js-sdk/blob/main/LICENSE). 
+- For more information about the license, see [MIT License](https://github.com/elasticpath/js-sdk/blob/main/LICENSE).