Feat: JsonLd product metadata (#2)

* Generates JSON ld structured metadata from a product & appends to head

* Updated IProduct & IVariation interface

* Added IProductResponse & IProductsResponse interfaces

* Fixed sitemap urls having to many protocols

src/routes/checkout/+page.svelte

@@ -7,7 +7,7 @@
   import VippsHurtigkasse from '$lib/components/VippsHurtigkasse.svelte';
   import { cart } from '$lib/cartStore';
 
-  import type IProduct from '$lib/interfaces/IProduct';
+  import type { IProduct } from '$lib/interfaces/IProduct';
 
   function postOrder(event: any) {
     const formData = new FormData(event.target);