Implement example playwright test

[stefanv]

We suspect that playwright may help to accelerate our test suit. It also has the following built-in features that we had to add manually to Selenium:

Auto-wait. Playwright waits for elements to be actionable prior to performing actions. It also has a rich set of introspection events. The combination of the two eliminates the need for artificial timeouts - the primary cause of flaky tests.

Web-first assertions. Playwright assertions are created specifically for the dynamic web. Checks are automatically retried until the necessary conditions are met.

Tracing. Configure test retry strategy, capture execution trace, videos, screenshots to eliminate flakes.

It includes a pytest plugin, so we can continue using our existing test fixtures.