[avatar] Inappropriate role #1614
Description
vaadin-avatar has role="button" by default, which indicates to screen readers that it is clickable, even though it is not interactive by default, nor does it have features to make it interactive (other than the possibility to attach clicklisteners that it shares with any other element).
A more appropriate default role would be role="img", with the exception of the overflow avatar in AvatarGroup, which should remain a button as it's clickable.
If collaboration engine uses the component in a way that makes it clickable, the role should probably be overriden back to "button". Consider introducing an API for setting the role.