updating gltfloader onAnimationGroupObservable calling

dist/preview release/viewer/babylon.viewer.d.ts

@@ -448,7 +448,7 @@ declare module BabylonViewer {
         constructor(scene: BABYLON.Scene, modelConfiguration: IModelConfiguration, disableAutoLoad: boolean);
         loader: BABYLON.ISceneLoaderPlugin | BABYLON.ISceneLoaderPluginAsync;
         meshes: Array<BABYLON.AbstractMesh>;
-        ootMesh: BABYLON.AbstractMesh;
+        rootMesh: BABYLON.AbstractMesh;
         particleSystems: Array<BABYLON.ParticleSystem>;
         skeletons: Array<BABYLON.Skeleton>;
         currentAnimation: IModelAnimation;

loaders/src/glTF/babylon.glTFFileLoader.ts

@@ -373,6 +373,7 @@ module BABYLON {
             loader.onTextureLoadedObservable.add(texture => this.onTextureLoadedObservable.notifyObservers(texture));
             loader.onMaterialLoadedObservable.add(material => this.onMaterialLoadedObservable.notifyObservers(material));
             loader.onExtensionLoadedObservable.add(extension => this.onExtensionLoadedObservable.notifyObservers(extension));
+            loader.onAnimationGroupLoadedObservable.add(animationGroup => this.onAnimationGroupLoadedObservable.notifyObservers(animationGroup));
 
             loader.onCompleteObservable.add(() => {
                 this.onMeshLoadedObservable.clear();