⚡ (engine) Improve engine overall robustness

packages/js/src/lib/gtag.ts

@@ -1,4 +1,4 @@
-import { GoogleAnalyticsOptions } from 'models'
+import type { GoogleAnalyticsOptions } from 'models'
 
 declare const gtag: (
   type: string,

packages/js/src/lib/stripe.ts

@@ -0,0 +1,13 @@
+import { Stripe } from '@stripe/stripe-js'
+
+export const loadStripe = (publishableKey: string): Promise<Stripe> =>
+  new Promise<Stripe>((resolve) => {
+    if (window.Stripe) return resolve(window.Stripe(publishableKey))
+    const script = document.createElement('script')
+    script.src = 'https://js.stripe.com/v3'
+    document.body.appendChild(script)
+    script.onload = () => {
+      if (!window.Stripe) throw new Error('Stripe.js failed to load.')
+      resolve(window.Stripe(publishableKey))
+    }
+  })