Add spelling TODOs

Summary: Ref T13005. Added reminders not to copy/paste.

Test Plan: None.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: epriestley, PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13005

Differential Revision: https://secure.phabricator.com/D18695