Add test for simple-carousel export path

### Completion criteria

In the second BWL video, we install this repo and use the simple carousel. To ensure this behavior doesn't break it may be useful to add a small test that checks that:

`npm install https://github.com/lit/video-series-samples.git`, followed by an `import 'video-series-samples/simple-carousel.js';` registers a simple-carousel to the window.
