app: Add modals and begin implementing donations

This patch adds a mechanism to open a modal, and roughs out a donation
flow using the 'braintree' payments provider.

src/components/App/App.tsx

@@ -2,6 +2,7 @@ import React, { Suspense } from "react";
 
 import "./App.css";
 import Header from "../Header/Header";
+import Modal from "../Modal/Modal";
 import Toolbar from "../Toolbar/Toolbar";
 import IconGrid from "../IconGrid/IconGrid";
 import Footer from "../Footer/Footer";
@@ -10,6 +11,7 @@ import Notice from "../Notice/Notice";
 import useIconParameters from "../../hooks/useIconParameters";
 
 const errorFallback = <Notice message="Search error" />;
+const paymentFallback = <Notice message="Could not connect to payments" />;
 const waitingFallback = <Notice type="none" message="" />;
 
 const App: React.FC<any> = () => {
@@ -26,6 +28,9 @@ const App: React.FC<any> = () => {
           </Suspense>
         </ErrorBoundary>
       </main>
+      <Suspense fallback={paymentFallback}>
+        <Modal />
+      </Suspense>
       <Footer />
     </React.StrictMode>
   );