feat: Image slide should support configurable BoxFit

[matthew-carroll]

The ImageSlide displays an image. It appears that the only display option is to shrink the image to fit in the available space, centered.

I'd like to be able to scale my image to fill all space (crop), and also control the alignment of the cropped image.

ImageSlide should support a BoxFit as well as an alignment.

[mkobuolys]

Good catch, completely agree.