make spatial extent explicit

[sirrice]

It will be convenient to have a consistent API (e.g., .ext or always having w,h,x,y) that signifies the spatial extent for a view and mark. That way, a view can be defined using any object that has a spatial extent as canvas, and a mark can always be treated as a view

[HasflarSonto]

I have successfully added a .ext to the mark attributes, it is able to successfully return the location as well as the width and the height of the mark. I've pushed this into the explicit extent branch.

the spatial extent can be accessed by:
console.log(mark.ext)
and the canvas can be accessed by:
console.log(c.ext)

below is an image of the new mark printed in console:

[HasflarSonto]

The extent is only being updated at the end of the rendering process because that's when the DOM elements actually exist to calculate bounding boxes.

Hence to log the mark extent I need to time out for a set period of time until after the mark renders or else it will return the default 0 for all extents. Working on a fix to this issue

setTimeout(() => {
console.log("Square extent:", vsquare.ext);
}, 100);