Firebase exception handling

[Tobbe]

When I tried to login with Firebase using GitHub no errors were shown on the site, but in the console I could see this message

{
  "code": "auth/account-exists-with-different-credential",
  "message": "An account already exists with the same email address but 
              different sign-in credentials. Sign in using a provider 
              associated with this email address.",
  "email": "t[...]@tlundberg.com",
  "providerId": "github.com",
  "signInMethod": "github.com",
  "oauthAccessToken": "b4a0ae573b[...]80e6f399a4a6"
}

I'm not sure how complete we need the auth example implementations to be. It is just a playground after all. But perhaps we should at least indicate that something went wrong. Maybe even say something like "See the dev console for more details"

What do you all think?

[dthyresson]

Related to issue https://github.com/redwoodjs/playground-auth/issues/39