Add usage example to the README

Author: pamil

README.md

@@ -21,3 +21,17 @@ Adds variadic arguments support to Behat steps definitions.
     ```
 
 3. Boom! :boom: Your Behat contexts are able to use variadic arguments in steps definitions!
+
+    ```php
+    /**
+     * @Given the store has( also) :firstProductName and :secondProductName products
+     * @Given the store has( also) :firstProductName, :secondProductName and :thirdProductName products
+     * @Given the store has( also) :firstProductName, :secondProductName, :thirdProductName and :fourthProductName products
+     */
+    public function theStoreHasProducts(...$productsNames)
+    {
+        foreach ($productsNames as $productName) {
+            $this->saveProduct($this->createProduct($productName));
+        }
+    }
+    ```