allow maxSize to accept an accessor function

[davelandry]

Expected Behavior

Would be great if the maxSize could be determined based on the available space. For example, when creating an AxisBottom, the user should be supplied the available height for the axis, and if they want to make the maxSize half of the proposed height, they would pass the following:

.maxSize(d => d / 2)

Where d is the value of the internal variable being used for the overall height.

Current Behavior

Currently, it expects a pixel value.