Fix missing material.skinning in GLTF2Loader

examples/js/loaders/GLTF2Loader.js

@@ -2013,6 +2013,7 @@ THREE.GLTF2Loader = ( function () {
 
 									var geometry = originalGeometry;
 									var material = originalMaterial;
+									material.skinning = true;
 
 									child = new THREE.SkinnedMesh( geometry, material, false );
 									child.castShadow = true;