readings for week 8 updated

Please do the following before merging.

• verify things look visually consistent.
• change ed post category from sustainability and cronick ilness to sustainability and games.
• post Ed post, or ping Venkatesh.
• update Ed link in schedule.md.
• update canvas assignment to reflect these readings.
• merge

schedule.md

@@ -341,7 +341,7 @@ Think of a part of a game you’ve played that is both a source of Difficulty AN
 Can you think of a potentially problematic effect in a game that you played? Why is it problematic? Is there an option to disable it?
 
 
-- **Required:  [Please post your response in this Ed thread]({site.discussion}/2649283)**
+- **Required:  [Please post your response in this Ed thread]({site.discussion}/3851117)**
 
 {: .homework} [Group Project Checkpoint](assignments/project-checkpoint.html) Assigned: Group Project Checkpoint
 :