R1:262edcc54232

Swap file upload icon on Remarkup Bar

Summary: It's a cloud, with an arrow. Serious. Business.

Test Plan: reload page. marvel at my photosynthesis skillz

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, aran

Maniphest Tasks: T3746

Differential Revision: https://secure.phabricator.com/D6947