Add the ability to get the resulting modified image with object bounds

[spullara]

This was done in a way so as not to change the public API in a non-breaking way.

[spullara]

Possible fix for: https://github.com/philipperemy/python-darknet-yolo-v4/issues/2

[philipperemy]

@spullara thank you will have a look soon :)

[philipperemy]

But in your case you can simply get the bounding boxes results back with the function and use any plotting library to display them no?

[spullara]

Sure, I could do it all separately without using the library.

[philipperemy]

Then probably better to do it on your side I think.