Added Auth0 and Classroom Sign-in Modes

Auth0 Support

See: https://mathewdunne.github.io/CodeRunner/deploying/oauth-credentials#set-up-auth0

Classroom Sign-in

• Lets students sign into temporary sessions with a 6 digit code and their name
• Useful for letting groups of students work on lessons when it may not be convenient for them to create/sign into google/github accounts and they don't need to save progress between sessions

See: https://mathewdunne.github.io/CodeRunner/operating/day-to-day#running-a-classroom-session

What's Changed

• Classroom join codes by @mathewdunne in #25
• feat(auth): Auth0 SSO sign-in by @mathewdunne in #26

Full Changelog: v0.6.3...v0.6.4