[EKS]: Manifests and charts for add-ons in a public repository

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**Tell us about your request**
Publish all add-on manifests in a single repo - ideally https://github.com/aws/eks-charts

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Today, manifest URLs are listed in the public EKS docs but there is no a public repo that contains them all in one place. This makes it hard to diff between add-on updates and ensure the latest changes are applied.

**Are you currently working around this issue?**
Downloading all chart/manifest versions and comparing them manually.

**Other information**
This resolves #266

Start by reviewing the public EKS documentation URLs and the proposed aws/eks-charts repository, then inventory the add-on manifests and chart versions that must be collected. Done means all add-on manifests are published together in one public repository and can be diffed across updates.

Written by the indexing model from the issue text.