ARCO-150: update changelog (#559)

CHANGELOG.md

@@ -22,6 +22,7 @@ All notable changes to this project will be documented in this file. The format
 ### Added
 - [Double Spend Detection](https://bitcoin-sv.github.io/arc/#/?id=double-spending) is a feature that introduces `DOUBLE_SPEND_ATTEMPTED` status to transactions that attempt double spend together with `CompetingTxs` field in the API responses and callbacks.
 - [Cumulative Fees Validation](https://bitcoin-sv.github.io/arc/#/?id=cumulative-fees-validation) is a feature that checks if a transaction has a sufficient fee not only for itself but also for all unmined ancestors that do not have sufficient fees.
+- [Multiple callbacks to single transaction](https://bitcoin-sv.github.io/arc/#/?id=callbacks) Is a feature that adds support for attaching multiple callbacks to a single transaction when submitting an existing transaction with a different data.
 
 ## [1.1.91] - 2024-06-26