Split CloudFormation and Terraform Documentation

[dumrauf]

With CloudFormation sort of becoming legacy at this point, it would make sense to split the documentation and move it into the respective sub-directories.

This would allow for a more independent development of the Terraform module. Plus, less clutter, which is always good.

[hkdobrev]

I imagine with this it would also be possible to register the Terraform module in the registry: https://registry.terraform.io/