Mark silent/printBackground as optional

docs/api/webview-tag.md

@@ -537,8 +537,8 @@ Stops any `findInPage` request for the `webview` with the provided `action`.
 ### `<webview>.print([options])`
 
 * `options` Object (optional)
-  * `silent` Boolean - Don't ask user for print settings. Default is `false`.
-  * `printBackground` Boolean - Also prints the background color and image of
+  * `silent` Boolean (optional) - Don't ask user for print settings. Default is `false`.
+  * `printBackground` Boolean (optional) - Also prints the background color and image of
     the web page. Default is `false`.
   * `deviceName` String (optional) - Set the printer device name to use. Default is `''`.