Add guidance on code snip continuation

Author: adellape

contributing_to_docs/doc_guidelines.adoc

@@ -514,6 +514,31 @@ $ oc get endpoints --all-namespaces --template \
 # subscription-manager list
 ----
 
+* For snippets or sections of a larger file, use an ellipsis (`...`) to show that
+the file continues before and/or after the quoted block:
++
+----
+apiVersion: v1
+kind: Pod
+metadata:
+  labels:
+    test: liveness
+...
+----
++
+or
++
+----
+...
+spec:
+  containers:
+  - args:
+    image: k8s.gcr.io/liveness
+...
+----
++
+Do not use `[...]`, `<snip>`, or any other variant.
+
 === Inline code or commands
 Do NOT show full commands or command syntax inline within a sentence. The next section covers how to show commands and command syntax.