Support sorting by depth in 2d picking module

[ViciousBadger]

Hello,

I was wondering if it was possible to use Avian2D's mesh picking plugin while sorting pickable meshes by the Z value of their global transform so that the "visible" object is picked in case of overlaps. in my case I often have entities with colliders "on top of" each other.

Of course I believe I could just use bevy's built in mesh picker plugin for this case, but it would be cool if Avian also supported this :)