Add pointer positions to zoom event

Hi,

currently zoom event properties include the scale and the direction. it will be very useful, if the pointer position will be added to.

the change is very simple to implement. in vis.js file, at the end of the "zoom" value function, change it to: if (scaleOld < scale) { this.body.emitter.emit('zoom', { direction: '+', scale: this.body.view.scale**, pointer: pointer** }); } else { this.body.emitter.emit('zoom', { direction: '-', scale: this.body.view.scale**, pointer: pointer** }); }

Thanks.