OSDOCS-12566: Add serverless to ROSA HCP

Author: bhardesty

_topic_maps/_topic_map_rosa_hcp.yml

@@ -903,3 +903,13 @@ Topics:
 #  Topics:
 #  - Name: Adding worker nodes to single-node OpenShift clusters
 #    File: nodes-sno-worker-nodes
+---
+Name: Serverless
+Dir: serverless
+Distros: openshift-rosa-hcp
+Topics:
+- Name: About Serverless
+  Dir: about
+  Topics:
+  - Name: Serverless overview
+    File: about-serverless