Listen to this event to determine when a user has logged in or out

Example:

window.addEventListener("supercast-login-state-changed", function(event) {
	if (event.detail == null) {
    console.log("User is logged out.");
  } else {
    console.log("User is logged in", event.detail);
  }
});

Returns:

A promise that resolves to an object containing information about the current user.