Interpolate hm intro (#228)

* Interpolation ApplyMatrixTransformations

* Fix scenefile saving and add skybox export

---------

Co-authored-by: MegaMech <7255464+MegaMech@users.noreply.github.com>

src/port/Game.cpp

@@ -141,7 +141,8 @@ void CustomEngineInit() {
     gWorldInstance.AddCup(gBattleCup);
 
     /* Set default course; mario raceway */
-    SelectMarioRaceway();
+    //SelectMarioRaceway(); // This results in a nullptr
+    gWorldInstance.CurrentCourse = mario;
     gWorldInstance.CurrentCup = gMushroomCup;
     gWorldInstance.CurrentCup->CursorPosition = 3;
     gWorldInstance.CupIndex = 0;
@@ -601,10 +602,6 @@ void* GetCourse(void) {
     return gWorldInstance.CurrentCourse;
 }
 
-void SetCourseByClass(void* course) {
-    gWorldInstance.CurrentCourse = (Course*) course;
-}
-
 struct Actor* CM_GetActor(size_t index) {
     if (index < gWorldInstance.Actors.size()) {
         AActor* actor = gWorldInstance.Actors[index];