Add existing to tracked

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

@@ -0,0 +1,39 @@
+// @ts-check
+
+/**
+ * The direction to display a primitive or ImageryLayer relative to the {@link Scene#splitPosition}.
+ *
+ * @enum {number}
+ *
+ * @see ImageryLayer#splitDirection
+ * @see Cesium3DTileset#splitDirection
+ */
+const SplitDirection = {
+  /**
+   * Display the primitive or ImageryLayer to the left of the {@link Scene#splitPosition}.
+   *
+   * @type {number}
+   * @constant
+   */
+  LEFT: -1.0,
+
+  /**
+   *  Always display the primitive or ImageryLayer.
+   *
+   * @type {number}
+   * @constant
+   */
+  NONE: 0.0,
+
+  /**
+   * Display the primitive or ImageryLayer to the right of the {@link Scene#splitPosition}.
+   *
+   * @type {number}
+   * @constant
+   */
+  RIGHT: 1.0,
+};
+
+Object.freeze(SplitDirection);
+
+export default SplitDirection;