allow cropping and preview for changing avatars

It's so frustrating changing your avatar on discord because you have to crop the picture itself to make sure what you want to show will fit in the circle. It would be really helpful if we could crop the photo when changing our avatar, and then if we could see a preview of the avatar in circle form before saving. You get timed out after two avatar changes and that's ridiculous considering I have to save it to see what it looks like in the first place.