Make Shopkit script location URL configurable (#53)

Author: petro97

src/App.tsx

@@ -13,7 +13,7 @@ import './App.scss';
 
 const App: React.FC = () => {
   useScript({
-    src: 'https://btn.moltin.com',
+    src: config.shopkitSrc,
     'data-moltin-client-id': config.clientId,
     'data-moltin-stripe-publishable-key': config.stripeKey
   });

src/config.ts

@@ -8,4 +8,5 @@ export const config = {
   algoliaApiKey: '7d829396bbf202b30bfe7ad52120bbac',
   algoliaIndexName: 'product',
   compareKeys: [],
+  shopkitSrc: 'https://btn.moltin.com',
 };