Process slowvote description as remarkup (link images, activate mentions, etc)
Summary: Fixes T10361.
Test Plan:
- Created a poll with an embedded file and a mention of a task.
- Verified file was attached properly.
- Verified mention appeared on task.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10361
Differential Revision: https://secure.phabricator.com/D15277