added diagram to readme

Author: Brad @ Redis

examples/postgres/k8s-docs/vault/README.md

@@ -12,4 +12,8 @@ vault write database/roles/redis-connect \
          ALTER USER \"{{name}}\" WITH SUPERUSER;" \
     default_ttl="24h" \
     max_ttl="24h"
-```
+```
+
+## Diagram
+
+!["Redis Connect in K8s with Vault"](redis-connect-k8s.png)