[contrib-guide] Updating url to doc-contrib-guide

Based off conversation at the PTG, we agreed it would be
beneficial to ensure the contrib-guide is clearly marked
as the doc contrib guide outside of the title.

This change includes a redirect.

Change-Id: I5abf915f0b94a482afa961e6b86364c26aae5d79

doc/doc-contrib-guide/source/diagram-guidelines/diagram-usage.rst

@@ -0,0 +1,36 @@
+.. _diagramusage:
+
+======================
+Use diagrams sparingly
+======================
+
+Diagrams can be useful tools to help orient users visualize complex
+processes. However, diagrams can sometimes be too simplistic, confusing
+the user instead of helping. The decision about whether a diagram is
+useful depends on the context of each project and the discretion
+of each contributor and reviewer.
+
+When to use diagrams
+~~~~~~~~~~~~~~~~~~~~
+
+Include diagrams in OpenStack documentation in the following
+situations:
+
+* If there is evidence of a process, whether the process is
+  automated or manual
+
+  Example: Basic setup workflow
+
+* If you need to clarify configurations and reference architectures
+
+  Example: Code review, upstream versus local environment
+
+
+When not to use diagrams
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Do not include diagrams in the following situations:
+
+* When a workflow is too simplistic
+* When there is no interaction with an OpenStack project
+* When a configuration can be easily explained through text