Add javascript test coverage

I plan to take a look at this. I see that at least resizing the browser window can be done using $this->getSession()->resizeWindow($width, $height, 'current');

I've taken a first step at writing the JS tests. The first implemented test runs fine locally, but checking for the element's position currently requires calling a method on the webdriver session object. Not sure if that would work on the test bot. I will create a merge request just to see if this kind of test works on the testbot.

I think that this is ready.

Thanks @MegaChriz! Awesome work! 1+ Will review asap.

Ooops! @alexpott was qicker! +1 :-) And it's in. Perfect.

Automatically closed - issue fixed for 2 weeks with no activity.