Convert touchscreen example to async

Author: inancgumus

examples/touchscreen.js

@@ -21,7 +21,7 @@ export default async function () {
   // Obtain ElementHandle for news link and navigate to it
   // by tapping in the 'a' element's bounding box
   const newsLinkBox = page.$('a[href="/news.php"]').boundingBox();
-  page.touchscreen.tap(newsLinkBox.x + newsLinkBox.width / 2, newsLinkBox.y);
+  await page.touchscreen.tap(newsLinkBox.x + newsLinkBox.width / 2, newsLinkBox.y);
 
   // Wait until the navigation is done before closing the page.
   // Otherwise, there will be a race condition between the page closing