SHOT-4439: Add new file handling for Nx File (.prt) (#137)

Author: staceyoue

env/includes/vred/apps.yml

@@ -50,6 +50,7 @@ vred.apps.tk-multi-loader2:
     Catpart File: [import, import_with_options]
     Fbx File: [import, import_with_options]
     Motion Builder FBX: [import, import_with_options]
+    Nx File: [import, import_with_options]
     VRED Scene: [import, import_with_options, import_as_env, smart_reference]
     Osb File: [import, import_with_options, import_as_env, smart_reference]
     Image: [ import_sceneplate ]