CHANGELOG: add patch for 1221

Author: dannywillems

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- **Makefile**: Add `run-block-producer` target with devnet/mainnet support and
+  `generate-block-producer-key` target for key generation
+  ([#1221](https://github.com/o1-labs/openmina/pull/1221)).
+
 ### Dependencies
 
 - bump proc-macro2 from 1.0.93 to 1.0.95