Add staff role/badge for instructors

[jwjulie]

Description: As a student, I want there to be an indicator that a user is an instructor and TA, so that I can identify if a post was made by teaching staff or a student.

Priority: High (3/10)

Justification: Easy/medium implementation difficulty level, but high impact on clarity for students. Being able to see at a glance the credibility of a post or question response makes parsing through a discussion or forum in general easier.

❗ NOTE: this proposed feature is no longer complex enough, #32 created and @yukiiii04 is now working on that for sprint 1.