R1:d4938c349be4

Applying (user )?monospace font to remarkup code blocks

Summary:
I feel that remarkup code blocks are still kind of small. This should help with my reading problems. Hesitating to add `.PhabricatorMonospaced` to the remarkup rule, since it's pretty specific to Phabricator.

Pasting in the diff btw, since my `arc`'s going crazy (doubt that's `arc.exe`, since it's not landed yet).

Test Plan:
Set font to something large. viewed code block. Was not large.

Applied change. Viewed code block again. It was…