Add the mandatory changelog to Marketplace add-ons

I wonder that no one requested this by far, so I am not sure if this will get enough points, but… Right now it is impossible to see what an add-on update really brings to you, unleast you are inspecting the add-on part by part. Many times the actual changelogs are only presented on the official websites or blogs of the creators. I think this is very crucial information that should be available first hand.