R1:06ae6194cca1

Allow ".ico" files to be viewed

Summary: No reason to keep these out of the defaults, can be useful in web stuff.

Test Plan: Uploaded, viewed a .ico file.

Reviewers: btrahan, paularmstrong

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1883