FedCM Demo Flow
0. If no one is logged into the Demo IdP, nothing will happen.
1. Login to the **Demo IdP**.
2. When you visit **Demo RP**, FedCM's `login()` is executed.
3. FedCM's `logout()` is executed when you click **SIGNOUT** button.
0. If no one is logged into the Demo IdP, nothing will happen.
1. Login to the **Demo IdP**.
2. When you visit **Demo RP**, FedCM's `login()` is executed.
3. FedCM's `logout()` is executed when you click **SIGNOUT** button.