Add acknowledgments for Shawn McKee contributions

Added acknowledgments section to release notes.

Author: kofemann

release-notes-11.2

@@ -72,6 +72,10 @@ HTML header: <title>dCache 11.2 Release Notes</title>
 
 - Xrootd PrepareRequest will return `Unsupported`.
 
+## Acknowledgments
+
+We want to thank Shawn McKee for his contributions.
+
 ## Release 11.2.2
 
 ### common