Summary: Spruce up the file embeds a little more, hover state, icons, file size.
Test Plan:
Add a psd and pdf, see new icons. Check differential, still see icons there too. Test mobile, desktop.
{F2042539}
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16950
