Add a sentence about cosign and supply chain security

Signed-off-by: Jirka Kremser <[email protected]>

self-assessment.md

@@ -24,3 +24,7 @@ Quick reference information, later used for indexing.
 | Security insights | https://github.com/k8gb-io/k8gb/blob/master/SECURITY-INSIGHTS.yml |
 | Cosign pub-key | https://github.com/k8gb-io/k8gb/blob/master/cosign.pub |
 
+### Intended Use
+
+To increase the software supply chain security, we encourage our users to consume k8gb container images with Kyverno's admission webhook that will ensure that
+images are signed and nobody had tempered with them. Our public key that can be used to verify this is in the root or our repository.