docs: integrate shipstation guide (#10623)

* first draft

* finalized first draft + added link to sidebar

* fix lint errors

* type changes

* updates to createFulfillment

* updates

* more updates

* add package weight

* added note about package

* fix up order items fulfillment

* add meta image

* address comment

www/apps/resources/app/js-sdk/page.mdx

@@ -315,8 +315,8 @@ For example, to send a request to a custom route at `http://localhost:9000/custo
   sdk.client.fetch(`/custom`, {
     method: "post",
     body: {
-      id: "123"
-    }
+      id: "123",
+    },
   }).then((data) => {
     console.log(data)
   })