Setup jest config and added example test.

test/basic.test.ts

@@ -0,0 +1,7 @@
+import {describe, expect, test} from '@jest/globals';
+
+describe('sum module', () => {
+  test('adds 1 + 2 to equal 3', () => {
+    expect(1 + 2).toBe(3);
+  });
+});