clayCredentials.json documentation for github users

[rtxanson]

Thinking it would be useful to provide some documentation for users who want to use clay-cli but authenticate through Git. The login process asks for a password, but I don't have one. I dug around and discovered the structure of clayCredentials.json, created my own auth token, and that works; doubtless someone else will want to find this.

[kareemamin]

Thanks for the note! That's definitely an issue and we'll be fixing that so you can login with the cli even if you authenticated through git. Glad you worked around this and we'll be fixing it right away.