add dummy function with todo

packages/core/test/splitLanes.test.mjs

@@ -0,0 +1,12 @@
+import { fastcat, stack, slowcat, silence, pure } from '../pattern.mjs';
+import { strict as assert } from 'assert';
+import splitLanes from '../splitLanes.mjs';
+
+describe('splitLanes', () => {
+  it('should split', () => {
+    const haps = fastcat(0, stack(1, 2))._firstCycleValues;
+
+    assert.deepStrictEqual(haps, [0, 1, 2]);
+    assert.deepStrictEqual(splitLanes([0, 1, 2]), [[0, 1, 2]]);
+  });
+});