Add blog simplify-kubernetes-operations-with-mutatingadmissionpolicy

[gardener-answering-machine]

Purpose:
@voelzmo This is an automatically generated draft pull request proposing a new blog post based on your Gardener review meeting presentation you gave on 2025-09-10 titled:

"Simplify Kubernetes Operations with MutatingAdmissionPolicy"

The purpose of the blog post is to actively inform the community about new Gardener features or changes, as discussed during review meetings.

Notes to Reviewers:
This draft was automatically generated by LLMs using the review meeting recording and referenced materials.
Please evaluate whether this topic is suitable for a blog post. If so, review and edit the content as needed.
If you decide the topic isn’t appropriate for a blog post, feel free to close this PR and delete the branch.

⚠️ This is an experimental GenAI feature. Feedback is welcome! Please direct it to @vlerenc. Thank you!

Instructions for Reviewers:

1. Clone the repository and change to the directory:

git clone https://github.com/gardener/documentation
cd documentation

2. Check out the branch:

git fetch origin && git checkout blog/2025-09-10-simplify-kubernetes-operations-with-mutatingadmissionpolicy

3. Review the content in website/blog/2025/09/09-10-simplify-kubernetes-operations-with-mutatingadmissionpolicy.md.
4. Make any necessary edits, additions, or removals and then push the changes:

git add website/blog/2025/09/09-10-simplify-kubernetes-operations-with-mutatingadmissionpolicy.md
git commit --amend --no-edit
git push origin +blog/2025-09-10-simplify-kubernetes-operations-with-mutatingadmissionpolicy

5. If the draft isn’t viable, close this PR and delete the branch.
6. If the post is ready for further review or publishing:
   • Mark this PR as Ready for review
   • Invite additional reviewers (optional)
   • Merge the PR (you take the decision; documentation-maintainers will not automatically review generated blog post PRs and will not merge them)

@voelzmo Thank you for helping us share valuable updates from the Gardener project with the community!