ft: refactor materials/texture decoupling

made it so all materials can use a texture for colour source. this
should be extendable if we want to do e.g. coded patterns in future

src/scenes/scene.rs

@@ -29,7 +29,7 @@ pub struct Scene {
     image_width: u32,
     image_height: u32,
 
-    // raytracing 
+    // raytracing
     max_depth: u32,
 }
 
@@ -79,7 +79,10 @@ impl Scene {
                         world.push(Arc::new(Sphere::new(
                             center,
                             0.2,
-                            Arc::new(Lambertian::new(ColourSource::Colour(Vec3::random() * Vec3::random()), 1.)),
+                            Arc::new(Lambertian::new(
+                                ColourSource::Colour(Vec3::random() * Vec3::random()),
+                                1.,
+                            )),
                         )));
                     } else if mat < 0.95 {
                         // metal
@@ -187,7 +190,7 @@ struct SceneDef {
     pub max_depth: u32,
 }
 
-// TODO (low priority): rn textures are tightly coupled to materials; what if we wnat different
+// TODO (low priority): rn textures are tightly coupled to materials; what if we want different
 // materials to share a texture? apply the same technique we used for decoupling materials/objects
 // on textures/materials.
 impl<'de> Deserialize<'de> for Scene {