Doc improvement for cluster_addons

[VardyNg]

Is your request related to a new offering from AWS?

Is this functionality available in the AWS provider for Terraform? See CHANGELOG.md, too.

• No 🛑: please wait to file a request until the functionality is avaialble in the AWS provider
• Yes ✅: please list the AWS provider version which introduced this functionality

Is your request related to a problem? Please describe.

I have been working on a project to provision EKS with Add-ons using the module.
While configuring cluster_addons, I found it is not easy to find the accepted plugin names list, I did some searching and testing and finally understand it is the Add-ons name defined in this AWS Doc

Describe the solution you'd like.

I think it would be great to add reference to this doc, so that others can know where to find the plugin name and supply to the cluster_addons

Describe alternatives you've considered.

NA

Additional context

NA