Add basic tempest run instructions to the quickstart

This commit adds details for using tempest run to execute tempest tests
to the quickstart guide in the readme.

Partially-implements: bp tempest-run-cmd

Change-Id: I7c5b51e4f055424fa62b1b262b2d1c96918e46eb
diff --git a/doc/source/run.rst b/doc/source/run.rst
index 07fa5f7..ce7f03e 100644
--- a/doc/source/run.rst
+++ b/doc/source/run.rst
@@ -1,3 +1,5 @@
+.. _tempest_run:
+
 -----------
 Tempest Run
 -----------