Sidebar course navigation - outline activities that need attention

Activities could be styled by score, similar to conditional formatting in a spreadsheet. Also would be good to style unanswered activities.

It would be nice if the lessons that aren't the current lesson could be collapsed also, if there's a long course it will be a huge block otherwise.

Done in 📌 [PP-1] Convert course navigation block to SDC Active -- does this need more attention / features?