fix readme

Author: Philip K

README.md

@@ -99,6 +99,7 @@ export default class App extends React.Component {
 | footerContainerStyle   | object<br><br>`{someStyle: someValue}`                                                 | no       | custom style props for container that will be holding your footer that you pass                                                                                                                                                      | `bottom: 0, position: "absolute", zIndex: 9999`           |
 | backgroundColor        | string<br><br>`white`                                                                  | no       | Component background color                                                                                                                                                                                                           | `black`                                                   |
 | enableSwipeDown        | boolean                                                                                | no       | Enable swipe down to close image viewer. When swipe down, will trigger onCancel.                                                                                                                                                     | false                                                     |
+| swipeDownThreshold     | number                                                                                 | no       | Threshold for firing swipe down function                                                                                                                                                                                             |                                                           |
 | doubleClickInterval    | number                                                                                 | no       | Double click interval.                                                                                                                                                                                                               |                                                           |
 | pageAnimateTime        | number                                                                                 | no       | Set the animation time for page flipping.                                                                                                                                                                                            | 100                                                       |
 | enablePreload          | boolean                                                                                | no       | Preload the next image                                                                                                                                                                                                               | false                                                     |