Include an example for the login flow

[Ross-Gibson]

After completing the setup, the bare-bones app currently displays a "Hello World!" message - this is great, as most of the services infrastructure is already in place, but since this project is highly reliant on Firebase and the Auth service, it could be beneficial to include this setup in the source. In short the example app could handle:

• Anonymous login (on mount)
• Ability to link an account via email/password, or any other the service providers
• A button to sign out
• A welcome screen (somewhere users are redirected after sign out, with the ability to sign in again)