A quick feature request -- it currently seems that I have to use the mouse to scroll horizontally in MetaPDF. It would be very helpful to be able to scroll horizontally with the arrow keys. I often read documents with multiple pages or columns that require horizontal scrolling, and it's a little annoying to have to grab the mouse each time. (I also recognize that this might be an issue with Chrome, not Paperpile--so any workaround tips would be appreciated.) Thanks for all your work!