Sidebar doesn't stick at the top

[respinos]

Description:

The sidebar on the scanned image page does not stick to the top when scrolling the page.

(Addendum: issue with IE (Edge and Not-Edge); the specifications are vague whether what we're doing is legal within display: table)

Acceptance Criteria:

• [ ] sidebar should stop at the top of the screen

[respinos]

See: https://webdesign.tutsplus.com/tutorials/sticky-positioning-with-nothing-but-css--cms-24042