add CII badging reference

adding reference to https://bestpractices.coreinfrastructure.org/projects/1718/badge
to index.rst for onap.readthedocs.io

Change-Id: Ic847a2988299135f60c7ea389de8e3c4bbf0ce31
Signed-off-by: Hansen, Tony (th1395) <th1395@att.com>
Issue-ID: DCAEGEN2-570
diff --git a/docs/index.rst b/docs/index.rst
index 4a3c848..1decaee 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -22,3 +22,5 @@
    ./sections/services/serviceindex.rst
    ./sections/release-notes.rst
 
+image:: https://bestpractices.coreinfrastructure.org/projects/1718/badge
+