Add email template for verified certificate date

Add example email to “Example Messages to Students” section of “Course
Launching Activities” (DOC-1100)

@mhoeber @srpearce @lamagnifica @mmacfarlane  please review -- thanks!
That makes the structure non-parallel ("that *you* can add to your college application, help you start a career, or help you get a better job or promotion"). How about this?

But sometimes, completing a course can help bolster your college application, jump-start your career, or lead to a better job. With a verified certificate of achievement from edX, you can show colleges, employers, and colleagues that you've completed a challenging course.