Hacktoberfest: Course Setup Checklist Makeover

Fixes: CNVS-16413

Updates the existing Course Setup Checklist pop-under
with nicer markup and styles.

Note: this change should NOT affect the other checklist
still in Canvas -- in the ePortfolios section. I left that
one alone because it works a little differently.

Test plan:
- Go to any course's main page in Canvas
- In the right-side list of links, click
  Course Setup Checklist.
- Make sure everything is working properly, just
  like it did in the old checklist.

Change-Id: I99dcb9ed6356e5b2ebf5905e4c6dd998e31a145b
Reviewed-on: https://gerrit.instructure.com/42874
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Product-Review: Colleen Palmer <colleen@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>