CSOAR-3990: Update changelog.md

Author: rishabhjain-eng

CHANGELOG.md

@@ -2,8 +2,9 @@
 * Add new change notes here
 DOCS:
 * Updated monitor documentation with a few trigger condition fields that were missing.
+* Added support to manage CSOAR playbooks.
 FEATURES:
-* **New Resource:** sumologic_azure_metrics_source (GH-710), macros (SUMO-260843)
+* **New Resource:** sumologic_azure_metrics_source (GH-710), macros (SUMO-260843), sumologic_csoar_playbook (CSOAR-3990)
 
 ## 3.1.5 (September 9, 2025)