Add Jest unit tests

[davidnmora]

No description provided.

[davidnmora]

One potential challenge to test:

React can still rerender the component instance using useD3AttrTransition during animation. When a parent component renders the children will be rendered too and this can happen during the animation. shouldComponentUpdate won't guard against that since Context updates can skip shouldComponentUpdate() = false component.

I would safeguard against it by returning partially modified (halfway through animation) attributes from useD3Transition if it happens. This way if React rerenders halfway through animation for any reason, it will still work