Add comment about that only obj with face normals work currentlY

src/main.rs

@@ -245,7 +245,9 @@ fn main() {
 
 
 /*
-* Generates world based on .obj mesh file passed by path
+* Generates world based on .obj mesh file passed by path.
+*
+* Currently only works for .obj files which contain face normals.
 */
 fn from_obj(path: &str) -> HittableList {
     let mut world = HittableList::new();