Migrate existing policies to Artifact Hub

[flavio]

Artifact Hub can now be used to list Kubewarden policies. We would like to publish all the policies that currently are on the Policy Hub over to Artifact Hub.

Things to do

• [x] Migrate policies: https://github.com/kubewarden/policy-hub/issues/195
• [x] Update the policy templates
  • [x] gatekeeper-policy-template
  • [x] go-policy-template
  • [x] opa-policy-template
  • [x] policy-rust-template
  • [x] swift-policy-template
• [x] Update the docs: https://github.com/kubewarden/docs/pull/134
• [x] Blog post: https://github.com/kubewarden/kubewarden.io/pull/118
• [x] #191
• [x] Reach out to Artifact Hub developers: ask if there's a way to show which policies have a container image signed via Sigstore. There's already something similar done for container images. See for example this container image, which has a "signed" badge next to its name -> DONE with https://github.com/artifacthub/hub/issues/2146

Acceptance criteria

When migrating a policy to Artifact Hub, we will use the simple repo layout like this one. There's going to be only a artifacthub-pkg.yml file inside of the root of the project.

Each repository should also have a artifacthub-repo.yml file inside of the root of the project. In this way the entry will be listed as "verified" by Artifact Hub UI.

[flavio]

This can be closed now