Document why use this vs passing GitHub OAuth token with GitHubOAuthenticator

[yuvipanda]

You could mimic the experience of using gh-scoped-creds by instead using github oauthenticator with your jupyterhub and passing the full oauth token. While it does improve usability, it's a pretty hard security trade-off. Let's document what the trade-off is so users can make an informed choice.

Definition of done

• Section added here about comparisoin with GitHubOAuthenticator
• A link is added from https://github.com/jupyterhub/oauthenticator/tree/main/examples/auth_state (and related documentation) to this comparison

[yuvipanda]

Based off some conversations with @agoose77