Export AppState type for custom onRedirectCallback's

[adamjmcgrath]

Export AppState type so it can be used in custom onRedirectCallback's

See

auth0-react/examples/cra-react-router/src/index.tsx

Lines 4 to 11 in a4c5f67

	import { Auth0Provider, AppState } from '@auth0/auth0-react';
	const onRedirectCallback = (appState: AppState) => {
	// If using a Hash Router, you need to use window.history.replaceState to
	// remove the `code` and `state` query parameters from the callback url.
	// window.history.replaceState({}, document.title, window.location.pathname);
	history.replace((appState && appState.returnTo) || window.location.pathname);
	};

Refrences

Fixes #119