add implementations for getPrimitiveCount/getBoundingBox on FFIFilamentApp

thermion_dart/lib/src/filament/src/implementation/ffi_filament_app.dart

@@ -1194,4 +1194,21 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
   Future setPriority(ThermionEntity entity, int priority) async {
     RenderableManager_setPriority(renderableManager, entity, priority);
   }
+
+  ///
+  ///
+  ///
+  Future<int> getPrimitiveCount(ThermionEntity entity) async {
+    return RenderableManager_getPrimitiveCount(renderableManager, entity);
+  }
+
+  ///
+  ///
+  ///
+  Future<Aabb3> getBoundingBox(ThermionEntity entity) async {
+    final bb = RenderableManager_getBoundingBox(renderableManager, entity);
+    return Aabb3.centerAndHalfExtents(
+        Vector3(bb.centerX, bb.centerY, bb.centerZ),
+        Vector3(bb.halfExtentX, bb.halfExtentY, bb.halfExtentZ));
+  }
 }

thermion_dart/lib/src/filament/src/interface/filament_app.dart

@@ -342,10 +342,19 @@ abstract class FilamentApp<T> {
   ///
   Future<Matrix4> getWorldTransform(ThermionEntity entity);
 
-  ///
-  ///
+  /// Sets the render priority for [entity].
+  /// [priority] should be be between 0 and 7, with 0 meaning highest priority 
+  /// (rendered first) and 7 meaning lowest priority (rendered last).
   ///
   Future setPriority(ThermionEntity entity, int priority);
 
+  /// Gets the number of primitives for [entity] (which is assumed to be 
+  /// have a renderable component attached)
+  ///
+  Future<int> getPrimitiveCount(ThermionEntity entity);
 
+  /// Gets the bounding box for [entity] (which is assumed to be 
+  /// have a renderable component attached).
+  ///
+  Future<Aabb3> getBoundingBox(ThermionEntity entity);
 }