Add some comments to the CRA example for hash routing (#45)

examples/cra-react-router/src/App.tsx

@@ -9,6 +9,7 @@ import { Error } from './Error';
 import { Loading } from './Loading';
 import { Users } from './Users';
 
+// Use `createHashHistory` to use hash routing
 export const history = createBrowserHistory();
 
 function App() {

examples/cra-react-router/src/ProtectedRoute.tsx

@@ -6,5 +6,11 @@ export const ProtectedRoute = ({
   component,
   ...args
 }: React.PropsWithChildren<any>) => (
-  <Route component={withAuthenticationRequired(component)} {...args} />
+  <Route
+    component={withAuthenticationRequired(component, {
+      // If using a Hash Router, you need to pass the hash fragment as `returnTo`
+      // returnTo: () => window.location.hash.substr(1),
+    })}
+    {...args}
+  />
 );

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

@@ -4,6 +4,9 @@ import App, { history } from './App';
 import { Auth0Provider } from '@auth0/auth0-react';
 
 const onRedirectCallback = (appState: any) => {
+  // 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);
 };