Adding Registration Form and Navigation

In this lesson, we want to do a few things:

1. Move our Login page into a separate file
2. Register Navigation in our app
3. Create a Registration page

Once we have done this, we should have interactable Screens (pages) in our app.

Note: We are still missing functionality.

Move the Login Page Into a Separate File

So far, we have written our code in lib/main.dart. This is not...