Add some usage guides to the tf registry docs

https://developer.hashicorp.com/terraform/registry/providers/docs#directory-structure

It's probably worth adding some more detailed setup guides for particular use-cases, rather than relying on being able to piece things together from individual resource examples.

Suggest initially setting up agents, for both jwt and public key mechanisms.

Start with the Terraform Registry provider documentation guidance at the linked directory-structure page and inspect this provider's existing registry docs. Add detailed usage guides for setting up agents with JWT and public-key mechanisms; done means both use cases are documented beyond the individual resource examples.

Written by the indexing model from the issue text.