R1:17cd119b91a5

Add inline styles for `{key ...}` in HTML mail

Summary: Fixes T11607.

Test Plan:
- Made a comment using `{key ...}`.
- Used `bin/mail show-outbound --id X --dump-html > test.html` to review HTML:

{F1805304}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11607

Differential Revision: https://secure.phabricator.com/D16523