async function scraper() {
    //...

    // set the browser options
    const options = new firefox.Options().addArguments('--headless');

    // initialize the webdriver
    const driver = new Builder()
        .forBrowser('firefox')
        // add the proxy to the webdriver
        .setProxy(proxy.manual({
            http: proxyString,
            https: proxyString,
        }))
        .setFirefoxOptions(options)
        .build();
}