FE: Demo User

[rajivtitus]

• Create a "demo user" functionality that will be used later to allow recruiters and managers to easily test the app's features without having to sign up
• Add a button to allow for signing in as a demo user
• This is effectively a login button with a hardcoded username and password
• Show button both on signup and login pages
• In production you should manually create a user and some test data that would best show off your project. Do this in development right now to test this feature