Describe the feature or problem you’d like to solve

I work on a GitHub Enterprise instance when using gh for work. My gh is only authenticated to the Enterprise instance and not public GitHub with a separate account (because #326). When I gh extension install vilmibm/gh-user-status, gh tries to install the extension by looking for this repo on the Enterprise instance. I had to explicitly gh extension install https://github.com/vilmibm/gh-user-status, which I didn't realize was possible at first glance of the docs.

Proposed solution

Update the docs to show both methods for installing an extension

1. Currently documented method , i.e. shorthand (vilmibm/gh-user-status)
2. Full link to repository (`https://github.com/vilmibm/gh-user-status

Additional context

N/A