Describe the feature or problem you’d like to solve

When I clone a fork with gh repo clone command, my only remote is the fork repo. It makes a lot of sense to also have a remote for the parent repo. As discussed in #582 (comment), we want to use the GitHub suggested remote naming conventions.

Proposed solution

After cloning a fork, automatically add a remote for the parent repo and name it upstream.

We should also automatically add the remote when someone uses gh repo fork and says they would like to clone the repo locally.