Update README

Author: zyc9012

README.md

@@ -114,6 +114,39 @@ await getJson({ engine: "google", q: "coffee" }); // uses the API key defined in
 await getJson({ engine: "google", api_key: API_KEY_2, q: "coffee" }); // API_KEY_2 will be used
 ```
 
+### Using a Proxy
+
+You can use a proxy by passing `requestOptions` with an `HttpsProxyAgent`
+instance. This can be done either globally through the config object or
+per-request in the parameters.
+
+First, install the required package:
+
+```bash
+npm install https-proxy-agent
+```
+
+Then use it in your code:
+
+```js
+import { config, getJson } from "serpapi";
+import { HttpsProxyAgent } from "https-proxy-agent";
+
+// Global configuration
+config.requestOptions = {
+  agent: new HttpsProxyAgent("http://proxy-server:port"),
+};
+
+// Or per-request configuration
+await getJson({
+  engine: "google",
+  q: "coffee",
+  requestOptions: {
+    agent: new HttpsProxyAgent("http://proxy-server:port"),
+  },
+});
+```
+
 ## Pagination
 
 Built-in pagination is not supported. Please refer to our pagination examples