Add a remarkup element for a navigation sequence

Summary: Fixes T4769. This is silly and just scratches an itch, but do a better job with navigation sequences.

Test Plan: {F195082}

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T4769

Differential Revision: https://secure.phabricator.com/D10353