Let the zoom behavior choose the appropriate transition duration?

[mbostock]

It might be nice if the zoom behavior set the transition duration by scaling the duration computed by d3.interpolateZoom. You’d need to have a multipler, though, like maybe you specify the duration as 250ms, but it means that’s the duration for a 2x zoom in-place, and it’s scaled accordingly for other transitions.

However, we’d need an option to disable this, since it’s equally valid for someone to specify the transition’s duration explicitly. Also, we might want to disambiguate between setting the duration of the dblclick transition and setting the duration of other zoom transitions.