Update Vendure provider to latest API changes (#352)

Relates to #349

framework/vendure/utils/mutations/adjust-order-line-mutation.ts

@@ -0,0 +1,15 @@
+import { cartFragment } from '../fragments/cart-fragment'
+
+export const adjustOrderLineMutation = /* GraphQL */ `
+  mutation adjustOrderLine($orderLineId: ID!, $quantity: Int!) {
+    adjustOrderLine(orderLineId: $orderLineId, quantity: $quantity) {
+      __typename
+      ...Cart
+      ... on ErrorResult {
+        errorCode
+        message
+      }
+    }
+  }
+  ${cartFragment}
+`