[breaking] Update CheckoutProvider to use new shape (#615)

This is to change `<CheckoutProvider />` to use https://js.stripe.com/clover/stripe.js

- options change from `fetchClientSecret: () => Promise<string>;` to `clientSecret: string | Promise<string>`
- `useCheckout` return the exact same object as https://github.com/stripe/react-stripe-js/releases/tag/v4.0.0

Author: pololi-stripe

package.json

@@ -93,7 +93,7 @@
     "@rollup/plugin-replace": "^5.0.5",
     "@rollup/plugin-terser": "^0.4.4",
     "@storybook/react": "^6.5.0-beta.8",
-    "@stripe/stripe-js": "^7.8.0",
+    "@stripe/stripe-js": "^8.0.0-rc.1",
     "@testing-library/jest-dom": "^5.16.4",
     "@testing-library/react": "^13.1.1",
     "@testing-library/react-hooks": "^8.0.0",
@@ -132,7 +132,7 @@
     "@types/react": "18.0.5"
   },
   "peerDependencies": {
-    "@stripe/stripe-js": ">=1.44.1 <8.0.0",
+    "@stripe/stripe-js": ">=8.0.0-rc.1 <9.0.0",
     "react": ">=16.8.0 <20.0.0",
     "react-dom": ">=16.8.0 <20.0.0"
   }