Write a guide how to integrate with Istio Service Mesh

[dadrus]

Preflight checklist

• [X] I agree to follow this project's Code of Conduct.
• [X] I have read and am following this repository's Contribution Guidelines."
• [X] I have discussed this feature request with the community.

Describe the background of your feature request

Istio extends Kubernetes to establish a programmable, application-aware network using the powerful Envoy service proxy, allowing integration external authorization services.

Describe your idea

Write a guide on how to achieve that with heimdall.