[FEAT] Add shadow support

apps/chapter_06.cpp

@@ -77,7 +77,8 @@ int shadow_sphere(uint8_t a_canvas_pixels, double a_wall_size, uint8_t a_wall_z)
                 Tuple the_point  = the_ray.position(the_intersec.distance_t());
                 Tuple the_normal = the_intersec.object().normal_at(the_point);
                 Tuple the_eye    = -the_ray.direction();
-                Color the_color  = the_intersec.object().material().lighting(the_light, the_point, the_eye, the_normal);
+                Color the_color =
+                    the_intersec.object().material().lighting(the_light, the_point, the_eye, the_normal, false);
                 the_canvas.write_pixel(x, y, the_color);
             }
         }