Added free5gc document link in FAQ

Change-Id: I36e7dd885efe1224b866c00bcb01099a9435134a
diff --git a/overview/faq.rst b/overview/faq.rst
index de1d803..96e438e 100644
--- a/overview/faq.rst
+++ b/overview/faq.rst
@@ -35,6 +35,7 @@
         * Transaction support in AMF & SMF
         * UE address allocation by UPF support at SMF
         * **There are many more changes done and above are just high level summary**
+        * Go through `google document link <https://docs.google.com/document/d/1B4WQdgK5QwLcsmgg9qMRP0lupawVzh1F8N5YjTpLBCM/edit#>`_ to get more details about changes.
 
     * **Network Performance Testing of SD-Core**