First version of Lightest operation

lightest1.go

func (c LightestOperation) Result(images []image.Image) (image.Image, error) {
	firstImage := images[0]
	bounds := firstImage.Bounds()
	lightest := image.NewRGBA(image.Rect(0, 0, bounds.Dx(), bounds.Dy()))
	draw.Draw(lightest, bounds, firstImage, bounds.Min, draw.Src)

	for _, currentImage := range images {
		if currentImage.Bounds() != bounds {
			return nil, errors.New("The images have different size!")
		}

		imageToCompare := image.NewRGBA(image.Rect(0, 0, bounds.Dx(), bounds.Dy()))
		draw.Draw(imageToCompare, bounds, currentImage, bounds.Min, draw.Src)
		c.getLightestImageBetweenTwo(lightest, imageToCompare)
	}

	return lightest, nil
}