Transitions / animations

Hello, this is a feature request, and I guess it's not an easy one :)

It would be great to be able to edit, translate, rotate or scale an existing shape dynamically, and interpolate this transformation over a custom amount of time.

Ex:

let ell = new Zdog.Ellipse({
  addTo: illo,
  diameter: 80,
  translate: { z: 40 },
  stroke: 20,
  color: '#636',
});

ell.animate({
  diameter: 150,
  translate: {z: -40},
  transition: "500ms",
});

// Result: the ellipse will change diameter from 80 to 150 and move from 40 to -40 in 500ms.

Bonus points if you manage to implement transition-timing-function too (linear, ease-in-and-out, etc)

Thanks, and congrats for this lib!