Add reference to OSA repo from main documentation page

In order to make it easy for users to find, let's add OSA reference
to the main page of ONAP documentation

Issue-ID: SECCOM-239
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Change-Id: I2c009a1a21289c2dd18f0e60122a24ec86aefb40
diff --git a/docs/index.rst b/docs/index.rst
index e1f7e24..619af5f 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -54,6 +54,9 @@
  |                                                                                 | and PNFs can accelerate the optimal usage of this ONAP environment. The guidelines            |
  |                                                                                 | on VNF/PNF requirements facilitates synchronized and aligned activities for all participants. |
  +---------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------+
+ | :ref:`ONAP Security <onap-security>`                                            | The current state of ONAP Security is described here. We can learn about discovered and fixed |
+ |                                                                                 | vulnerabilities.                                                                              |
+ +---------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------+
 
 
 .. toctree::