Update readme

README.md

@@ -135,6 +135,51 @@ if err != nil {
 }
 ```
 
+## Create a variant to a product
+
+If you want to create a new variant, you can do so using the following function. The ID of the main product is required.
+
+You can find the description from Shopify [here](https://shopify.dev/api/admin-rest/2021-07/resources/product-variant#[post]/admin/api/2021-07/products/{product_id}/variants.json).
+
+```go
+// Define request
+r := goshopify.Request{
+    ApiKey:      "",
+    ApiPassword: "",
+    StoreName:   "",
+}
+
+// Define body
+body := ProductVariantBody{
+    ProductVariantBodyVariant{
+        Title:               "Testartikel",
+        Price:               "24,99",
+        Sku:                 "21481462121",
+        CompareAtPrice:      "48,99",
+        FulfillmentService:  "manual",
+        InventoryManagement: "shopify",
+        Option1:             "42",
+        Option2:             "",
+        Option3:             "",
+        Taxable:             true,
+        Barcode:             "",
+        Grams:               0,
+        Weight:              0,
+        WeightUnit:          "",
+        InventoryQuantity:   0,
+        RequiresShipping:    true,
+    },
+}
+
+// Create a product variant
+variant, err := goshopify.AddProductVariant(6917353078968, body, r)
+if err != nil {
+    fmt.Println(err)
+} else {
+    fmt.Println(variant)
+}
+```
+
 ## Get list of orders since id
 
 To get a list of orders, you can call the following function. The list shows all orders by a certain ID, if you leave this ID at 0, then the orders are displayed from the beginning. 200 orders are always read out at once.