RDK-37090:Cobalt Document Update

Reason for change: Documentation Enhancement for Cobalt plugin
Test Procedure: Executing Cobalt curl commands
Risks: Create None
Signed-off-by: Sivapriya Venkatesan <Sivapriya_Venkatesan@comcast.com>
Change-Id: I56cc6643b16b610930f6a851135902395ac0d84b