This provider is no longer maintained - add deprecation warning to code

[deniseyu]

Hi folks,

This repo is no longer actively maintained by HashiCorp. We are in the process of archiving it - we recommend against critical path usage.

---

Notes for the DevRel team below:

In order to emit a deprecation message on terraform plan, we can add a message on the provider schema: https://github.com/hashicorp/terraform-plugin-framework/blob/69c808014c60330df8afc4fc2aeba2a19d20dafd/provider/schema/schema.go#L49-L59

Example snippets from the template provider when we deprecated it:
When the template provider was deprecated, looks like the registry documentation was updated along with the readme and a GitHub issue:
hashicorp/terraform-provider-template#84
hashicorp/terraform-provider-template#85

To display a warning on all runs, you can add it to the assert provider here:

	resp.Schema = schema.Schema{
		DeprecationMessage: "👋 This is not the provider you are looking for.. 👋",
		Attributes: map[string]schema.Attribute{},
	}