Next.js Commerce refresh. (#966)

We're making some updates to Next.js Commerce. Everything prior to this commit marks what we're calling [`v1`](https://github.com/vercel/commerce/releases/tag/v1) as a point in time to be able to reference and still use going into the future. The current architecture of Commerce is a multi-vendor, interoperable solution, including:

- [Shopify](https://shopify.vercel.store/)
- [Swell](https://swell.vercel.store/)
- [BigCommerce](https://bigcommerce.vercel.store/)
- [Vendure](https://vendure.vercel.store/)
- [Saleor](https://saleor.vercel.store/)
- [Ordercloud](https://ordercloud.vercel.store/)
- [Spree](https://spree.vercel.store/)
- [Kibo Commerce](https://kibocommerce.vercel.store/)
- [Commerce.js](https://commercejs.vercel.store/)
- [SalesForce Cloud Commerce](https://salesforce-cloud-commerce.vercel.store/)

All features can be toggled on or off, and it's easy to change between commerce providers. To support this, we needed to create a ["commerce metaframework"](d1d9e8c434/packages/commerce/new-provider.md) where providers could confirm to an API spec to add support for Next.js Commerce. While this worked and was successful for `v1`, we have different design goals and ambitions for `v2`.

**What You Need To Know**

- `v1` will not be updated moving forward. If you need to reference `v1`, you will still be able to clone and deploy the version tagged at this release.
- `v2` will be shifting to be a single provider vs. provider agnostic. Other providers are welcome to fork this repository and swap out the underlying `lib/` implementation that connects to the selected commerce provider (Shopify). This architecture was chosen to reduce the surface area of the codebase, remove the intermediate metaframework layer for provider-interoperability, and enable usage with the latest Next.js and React features.
- We will be sharing more about `v2` in the future as we continue to iterate before the marked release.

lib/shopify/queries/product.ts

@@ -0,0 +1,32 @@
+import productFragment from '../fragments/product';
+
+export const getProductQuery = /* GraphQL */ `
+  query getProduct($handle: String!) {
+    product(handle: $handle) {
+      ...product
+    }
+  }
+  ${productFragment}
+`;
+
+export const getProductsQuery = /* GraphQL */ `
+  query getProducts($sortKey: ProductSortKeys, $reverse: Boolean, $query: String) {
+    products(sortKey: $sortKey, reverse: $reverse, query: $query, first: 100) {
+      edges {
+        node {
+          ...product
+        }
+      }
+    }
+  }
+  ${productFragment}
+`;
+
+export const getProductRecommendationsQuery = /* GraphQL */ `
+  query getProductRecommendations($productId: ID!) {
+    productRecommendations(productId: $productId) {
+      ...product
+    }
+  }
+  ${productFragment}
+`;