cesium 添加gltf 配置项

var viewer = new Cesium.Viewer('cesiumContainer');
var entity = viewer.entities.add({
    name : 'gltf model',
    position: Cesium.Cartesian3.fromDegrees(-123.0744619, 44.0503706, 1000),
    model : {
        uri : 'path/to/your.gltf'
    }
});