Merge pull request #30424 from MikeRayMSFT/40419-add-release-note

Add introduction to arc data release notes

Author: prmerger-automator[bot]

docs/sql-server/azure-arc/release-notes.md

@@ -13,6 +13,15 @@ ms.custom: ignite-2023
 
 [!INCLUDE [sqlserver](../../includes/applies-to-version/sqlserver.md)]
 
+This article lists:
+
+- Release dates
+- Extension version numbers
+- High level feature descriptions
+- Links to additional feature documentation
+
+Extension versions are cumulative. Higher extension versions include all of the updates from previous versions. A release may include internal features. If the version release notes don't describe features, then the updates were internal.
+
 ## April 16, 2024
 
 **Extension version**: `1.1.2656.138`