Update README

Author: zyc9012

README.md

@@ -26,7 +26,8 @@ npm install serpapi
 
 ```js
 const { getJson } = require("serpapi");
-getJson("google", {
+getJson({
+  engine: "google",
   api_key: API_KEY, // Get your API_KEY from https://serpapi.com/manage-api-key
   q: "coffee",
   location: "Austin, Texas",