docs(readme): add "do not use in production" disclaimer

Author: waynevanson

README.md

@@ -4,6 +4,8 @@ React bindings to [SortableJS](https://github.com/SortableJS/Sortable)
 
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 
+Please note that this is not considered ready for production, as there are still a number of bugs being sent through.
+
 ## Features
 
 ## Installation