Keyboard Shortcuts for Going Backward/Forward 5 Seconds

Please add the keyboard shortcuts, left and right arrow keys, for going backward and forward 5 seconds of video, just like YouTube. Thanks.

@kushaangupta Thanks. However, you are talking about "VLC for Windows." I am talking about "VLC for Windows Store (VLC-WinRT)." Those hotkeys don't work in VLC-WinRT.

closed via commit 477e750b

Thanks, Martin.

mentioned in commit 26334e09