Currently you cannot add/customize the shortcut for scrolling down and up through a page. I would really like to be able to use j to scroll down and k to scroll up, as in the vim editor to browse. Almost every other browser function is customizable so I feel like this one was just overlooked.
Being able to browse pages like I navigate files in vim without needing the mouse would be a boon to programmers like me.
Personally I'd prefer it function like the down and up arrows on the keyboard, rather than page down/page up.