Add an embedded / customised example

[rishabhpoddar]

Add an example that:

• renders a custom footer and header across all the components of emailpassword recipe.
• Show logo on sign in / up UI
• Adds login UI to /login
• Adds sign up UI to /signup
• Adds a background to the login UI
• If already logged in, and we visit the auth pages, it should show some custom content, and not just redirect the user.

Example app: https://emailpassword.demo.supertokens.io/