Define policy and process for accepting repos in crossplane-contrib

[jbw976]

As per the Crossplane governance, the crossplane-contrib organization falls under the same governance as the main crossplane org and "exists to provide a neutral home for Crossplane extensions".

As new contributions/repos within the ecosystem continue to grow, we should take the time to define the process/policy/workflow for how we accept these new repos. This will help reduce confusion within the community, help them be more self-service, and expedite the process more quickly.

Typically, a repo is added in 1 of 2 ways:

1. a crossplane-contrib org admin is added as an admin to the new source repo, then they initiate the transfer since they are an admin on both sides
2. a new blank repo is created by an org admin, then the source repo owner opens the 1st PR to the new repo with the content.

We should document, explain, and improve all of this. A good potential home for this may be in a new crossplane-contrib/org repo.