Add border, transparent indicators to images in file property view

Summary: Fixes T3950. This centers the images, adds a thin blue border, and a transparent background.

Test Plan: Tested a file in Files, Diffusion, and Macro.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T3950

Differential Revision: https://secure.phabricator.com/D7305