Add existing to tracked

node_modules/@cesium/engine/Source/Scene/ModelAnimationLoop.js

@@ -0,0 +1,38 @@
+// @ts-check
+
+/**
+ * Determines if and how a glTF animation is looped.
+ *
+ * @enum {number}
+ *
+ * @see ModelAnimationCollection#add
+ */
+const ModelAnimationLoop = {
+  /**
+   * Play the animation once; do not loop it.
+   *
+   * @type {number}
+   * @constant
+   */
+  NONE: 0,
+
+  /**
+   * Loop the animation playing it from the start immediately after it stops.
+   *
+   * @type {number}
+   * @constant
+   */
+  REPEAT: 1,
+
+  /**
+   * Loop the animation.  First, playing it forward, then in reverse, then forward, and so on.
+   *
+   * @type {number}
+   * @constant
+   */
+  MIRRORED_REPEAT: 2,
+};
+
+Object.freeze(ModelAnimationLoop);
+
+export default ModelAnimationLoop;