docs(nginx-system): Update docs about the kube-proxy situation

infrastructure/nginx-system/README.md

@@ -3,6 +3,11 @@ nginx-system
 
 This component provides `ingress-nginx` as ingress solution to the cluster. It comes with some improved defaults, e.g. deploying a WAF by default.
 
+Nice to knows
+---
+
+- You have to enabled [`externalTrafficPolicy`](https://kubernetes.github.io/ingress-nginx/deploy/baremetal/#over-a-nodeport-service) to allow [`nginx.ingress.kubernetes.io/whitelist-source-range`](https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/annotations/#whitelist-source-range)
+
 Links
 ---