Missing documentation for that EKS VPC Endpoint is required for private cluster

[kangsheng89]

Describe the bug
AppMesh Private EKS cluster required EKS VPC endpoint. Missing documentation for this. The main.go will call eks.describeCluster during startup. Without adding EKS VPCE, the controller will crash with exit 2 error.

Steps to reproduce

Expected outcome
A concise description of what you expected to happen.

Environment

• App Mesh controller version
• Envoy version
• Are you using any integrations? X-ray, Jaeger etc. If so versions?
• Kubernetes version
• Using EKS (yes/no), if so version?

Additional Context: