build: add jest, tests

tests/splitIntoChunks.test.ts

@@ -0,0 +1,14 @@
+import { expect, test } from "@jest/globals";
+import { splitIntoChunks } from "../src";
+
+test("splits an array into chunks", () => {
+  // JSON.stringify is being used because there is no way to compare nested arrays in jest
+  expect(
+    JSON.stringify(splitIntoChunks(["a", "b", "c", "d", "e", "f"], 3)),
+  ).toBe(
+    JSON.stringify([
+      ["a", "b", "c"],
+      ["d", "e", "f"],
+    ]),
+  );
+});