wip: Traefik guide update

[dadrus]

Related issue(s)

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Checklist

• [x] I agree to follow this project's Code of Conduct.
• [x] I have read, and I am following this repository's Contributing Guidelines.
• [x] I have read the Security Policy.
• [x] I have referenced an issue describing the bug/feature request.
• [ ] I have added tests that prove the correctness of my implementation.
• [ ] I have updated the documentation.

Description

This PR updates the existing traefik guide and

• describes integration options using Ingress and IngressRoute in more details, and
• adds further integration options using the new Gateway API.

It also updates the docker examples to use the new v3.0.0 version of traefik and adds new examples for kubernetes.