Improve GitHub Rate Limit handling

[emilpaw]

I tried to use a template with create-remix but got following error message:
▲ Oh no! There was a problem fetching the file from GitHub. The request responded with a 403 status. Please try again later.

This message didn't help much, so I dug around and found out I was actually rate limited by GitHub for some reason.

My proposal is to read the x-ratelimit-remaining header on failed GitHub requests and based on that print an error message saying that the request was rate limited and that adding a personal access token might help.

Also, looking for a way to authenticate myself with GitHub, I noticed that there is the --token CLI argument, but it's missing in the --help output.

I'd be happy to contribute those improvements.

[emilpaw]

This could also been the issue in #7721.