adding common-attributes to the conventions

Author: kalexand-rh

modules/mod-docs-ocp-conventions.adoc

@@ -37,6 +37,11 @@ Example:
 :context: assembly-gsg
 ----
 
+* All assemblies must include the `modules/common-attributes.adoc` file near the
+context statement. This file contains the standard attributes for the collection.
++
+`include::modules/common-attributes.adoc[leveloffset=+1]`
+
 * All anchor ids must follow the format:
 +
 ----