Added a new property for ability to add some custom Overlay

[ivanstnsk]

How to use it now:

                <ImageCrop 
                    ref={'cropper'}
                    image={IMAGE_PATH}
                    cropWidth={292}
                    cropHeight={202}
                    zoom={50}
                    maxZoom={80}
                    minZoom={20}
                    panToMove={true}
                    pinchToZoom={true}
                    Overlay={(
                        <MyAwesomeOverlay />
                    )}
                />

Result:

👍

[ivanstnsk]

@stoffern just the feature I was needed on my current project :)