Draft: Ease github mirroring

TODO:

• Fail if initial mirroring fails

changed the description

Tested with https://gitlab.archlinux.org/archlinux/arch-boxes which had broken github mirroring for 2 years.

I will investigate if we can use the github terraform propvider for handling the configuration on the github side, instead of ClickOps.

What a bummer. "Disable Packages and Environments from being shown on the main page." cannot be controlled with Terraform :/

I have opened a issue upstream: https://github.com/integrations/terraform-provider-github/issues/2471.

requested review from @anthraxx