Have a way for reviewer to jump to start of next / previous submissions

[kondanna]

Right now, if there are more than two submissions pending review, it's difficult to navigate between them.

Perhaps a side nav bar as follows:

• <Challenge Title> -
• <Challenge Title> -
• ... and so on

the side nav follows the scrolling, and can just be numbers or dots (shorter that way), while the text only displays when hovering over the number.