Terraform examples

It'd be great if there were examples of using pkl instead of HCL for Terraform in the same way that there is [pkl-k8s-examples](https://github.com/apple/pkl-k8s-examples).

Start by reviewing the linked pkl-k8s-examples project and the repository's existing example structure. Add comparable examples showing how to use pkl instead of HCL for Terraform, with enough coverage to demonstrate the intended workflow. Done means the examples are present, coherent, and usable as a reference for Terraform users.

Written by the indexing model from the issue text.