Implement custom checkout (#487)

* Implement custom checkout core

* Fix elements on core

* Add files to providers

* Adapt providers

* Update types

* Update shopify file

* Format files

framework/swell/checkout/use-checkout.tsx

@@ -0,0 +1,14 @@
+import { SWRHook } from '@commerce/utils/types'
+import useCheckout, { UseCheckout } from '@commerce/checkout/use-checkout'
+
+export default useCheckout as UseCheckout<typeof handler>
+
+export const handler: SWRHook<any> = {
+  fetchOptions: {
+    query: '',
+  },
+  async fetcher({ input, options, fetch }) {},
+  useHook:
+    ({ useData }) =>
+    async (input) => ({}),
+}