adding stub for v3 versus v4 content

Author: kalexand-rh

_topic_map.yml

@@ -68,6 +68,13 @@ Topics:
 - Name: OpenShift CCS modular docs conventions
   File: mod-docs-conventions-ocp
 ---
+Name: Release notes
+Dir: release_notes
+Distros: openshift-enterprise
+Topics:
+- Name: Comparing OpenShift Container Platform v3 and v4
+  File: comparing_v3_v4
+---
 Name: Architecture
 Dir: architecture
 Distros: openshift-*
@@ -228,7 +235,7 @@ Name: Nodes
 Dir: nodes
 Distros: openshift-*
 Topics:
-- Name: About Pods 
+- Name: About Pods
   File: nodes-pods-using
 - Name: Viewing Pods
   File: nodes-pods-viewing

release_notes/comparing_v3_v4.adoc

@@ -0,0 +1,11 @@
+[id='architecture']
+= Comparing {product-title} v3 and v4
+include::modules/common-attributes.adoc[]
+:context: comparing_v3_v4
+toc::[]
+
+[IMPORTANT]
+====
+This is a placeholder for the high-level information about {product-title} v4 that is
+new and different from v3. Final placement in the TOC TBD.
+====

release_notes/images

@@ -0,0 +1 @@
+../images

release_notes/modules

@@ -0,0 +1 @@
+../modules