Add automated tests using playwright

[brollb]

I added some stubbed out tests to be added. Basically, it would be great to have some tests for each type of control. I imagine the playwright tests could

1. simply view the same playground that is hosted on GH pages
2. set the schema and uiSchema then run the test (probably should use some utilities to avoid too much code dupe there)
3. check the output in the third window (or download and check in the ignoreEmpty case)

@romancow - Can you take it from here?