Ceph: updates CephCluster CRD doc to include monitoring options
Ceph: updates CephCluster CRD doc to include monitoring options

adds documentation on spec to enable/disable monitoring of Ceph
clusters using prometheus. prometheus still needs to be deployed
separately.

Signed-off-by: Umanga Chapagain <078ce6f6b416ac444a5caae3922c36dd4ff12c22@gmail.com>

rook/rook,rook/rook,rook/nfs,rook/nfs,rook/rook,rook/nfs,rook/rook,rook/rook