[Feat] Send Certificate to User Email

[tayormi]

On completion of a track, user becomes a mentor. A certificate of completion should be sent to the user. Also a welcome email as a mentor is sent to the user as well.

[ofuochi]

I need an html/css template for this

[tayormi]

I'll find someone to create HTML file for the certificate.
For now, can you use any template you can find online so it doesn't stop your work?