Add eks-version-upgrade-readiness custom transformation

[brunokktro]

Summary

Adds a new community-sourced custom transformation for AWS Transform: EKS Version Upgrade Readiness.

Analyzes and transforms Kubernetes manifests, Helm charts, Kustomize overlays, Terraform, and AWS CDK code for compatibility with a target Amazon EKS/Kubernetes version. It detects removed/deprecated APIs, updates apiVersion fields and resource structures, validates addon compatibility, and generates a MIGRATION_REPORT.md with manual action items and a documented sequential upgrade path.

This complements (does not duplicate) cluster-upgrade orchestration tools — it focuses exclusively on the code that runs on the cluster, not the cluster upgrade execution itself.

What's included

community-sourced-transformations/eks-version-upgrade-readiness/
├── README.md                              # Overview, usage, atx publish/exec commands
├── SKILL.md                                # Skill definition (objective, scope, workflow, exit criteria)
└── references/
    ├── api-removals-by-version.md          # K8s API removal table, v1.16-v1.36 + quick lookup
    ├── eks-specific-changes.md             # Amazon EKS-specific changes, addon compatibility matrix
    └── examples-before-after.md            # 8 concrete before/after transformation examples

Testing

• Content validated against the official Kubernetes API deprecation guide and Amazon EKS release notes for version-specific changes (AL2 AMI deprecation, StorageClass defaults, IAM requirements, addon minimum versions).
• Followed the same README/SKILL.md/references structure as the existing jboss-to-springboot and kubernetes-readiness-migration samples in this directory.
• Not yet run end-to-end via atx custom def exec against a live customer repo — happy to iterate on structure/content based on maintainer feedback.

Notes

• No breaking changes to existing samples; this is a new, isolated directory under community-sourced-transformations/.