ability to print auth token #1514

It is sometimes desirable for a user to see the token gh uses for a given host. Right now they'd need to do one of two things:

• cat ~/.config/gh/hosts.yml
• gh config get -h github.com oauth_token

Neither of these is perfect, so this issue covers adding something to gh auth status like:

✓ Token: *******************

and supporting a flag --show-token/-t that prints the actual token value.

I'm also imagining nontty support like this:

gh auth status -h github.com -t >mytoken.txt