Prepare repository for publishing to the Terraform Registry

[lesteenman]

This PR makes the changes I believe to be necessary to perform deployments to build releases that are compatible with the Terraform Registry.

I've followed the steps myself already on my forked version of this repository to verify the steps should be correct. The resulting provider can be found at https://registry.terraform.io/providers/lesteenman/qbee-lesteenman/latest. I've tried my best to make it clear this is not the official version of this provider, and I will attempt to add a link to the official provider once it's available in its description to make it even more clear.

After merging this PR, the following steps are required to be taken manually.

Set up Github repository

Follow the steps in https://developer.hashicorp.com/terraform/registry/providers/publishing#github-actions-preferred . The PR already includes steps 3 (goreleaser configuration) and 4 (github workflow file). The other steps are required to make signed releases to Github.

The steps involve:

• Generate a GPG key (can be done on your local machine)
• Copy the private part of that key to your github repo's secrets

Publish to the Registry

Follow the steps at https://developer.hashicorp.com/terraform/registry/providers/publishing#publishing-to-the-registry

These steps involve:

• Log in to the Registry with your Github account
• Paste the public part of the generated GPG key so they can verify the authenticity of the builds
• Click "publish"

These steps have taken me minutes to do for my own fork, assuming you already have GPG installed.