Create Javascript tests

MR!15 is ready for a review.

Thanks @ankitv18 for this, I see a deprecation warning, I'll look into this, but it looks ok.

The method $this->assertSession()->statusCodeEquals(200) is deprecated and some cases it was failing on me, so I had to delete it.

Using PHPUnit 11.5.34 and PHP 8.4.10 for the tests.

Thanks again, I'll merge to the 2.0.x branch.