Add support for 2D poses with game piece objects

[blaze-developer]

I am localizing note positions in a 2D space. I noticed that when logging a note using a Pose2d, the note's origin is the very center of the note. However, if someone is only logging a 2D pose, would it be safe to assume that the note is lying on the ground and not inside the ground? Adding an offset would make user code more readable by simply not having to add an offset to every logged value.

[jwbonner]

To be clear, AdvantageScope doesn't currently support visualizing game piece objects using 2D poses (only 3D poses, transforms, and translations). If we added support for displaying game pieces using 2D poses, I agree that this would be a sensible way to do it.