Creates the 4.12 RN stub in main branch

Author: opayne1

release_notes/ocp-4-12-release-notes.adoc

@@ -0,0 +1,11 @@
+[id="ocp-4-12-release-notes"]
+= {product-title} {product-version} release notes
+include::_attributes/common-attributes.adoc[]
+:context: release-notes
+
+Do not add or edit release notes here. Edit release notes directly in the branch
+that they are relevant for.
+
+Release note changes should be added/edited in their own PR.
+
+This file is here to allow builds to work.