Published story: additional images should open inline with scroll/gallery view

[maebeale]

Problem

Clicking an additional image on a published story navigates away, and there's no way to scroll through the additional images as a set.

Proposal

• Clicking an additional image opens it in the same window (e.g., in a lightbox/modal)
• Provide next/previous controls so the user can scroll through all additional images for that story