Plaid Get incremental transaction updates on an Item

The `/transactions/sync` endpoint allows developers to subscribe to all transactions associated with an Item and get updates synchronously in a stream-like manner, using a cursor to track which updates have already been seen. `/transactions/sync` provides the same functionality as `/transactions/get` and can be used instead of `/transactions/get` to simplify the process of tracking transactions updates. To learn more about migrating from `/transactions/get`, see the [Transactions Sync migrat...