Added link to qunit-helpful

Added link to [qunit-helpful](https://github.com/bahmutov/qunit-helpful) - adds the actual expression that failed the assertion to the error message

```js
// QUnit test with failing assertion
QUnit.test('simple test', function () {
  ok(2 + 2 === 5);
});

// output
  Errors:
    Module: global Test: simple test

// load qunit-helpful.js before tests, same test
// output
  Errors: ok [2 + 2 === 5]
    Module: global Test: simple test
```