examples: Explain operator manifest role
examples: Explain operator manifest role

This helps explain why there are two manifests to deploy the operator
(this one and the one under `examples/rbac/habitat-operator.yml`).

Signed-off-by: Lorenzo Manacorda <86995a091f8a1385082bd10715048b52ee386a6a@kinvolk.io>

kinvolk/habitat-operator,kinvolk/habitat-operator