Coverage support

[pamelafox]

I am wondering if there's any possibility of seeing coverage for the frontend JS files when we run pytest-playwright. I assume not, but want to confirm before I write off the possibility.

[mxschmitt]

There is no out of the box solution. It can be done in the user land like here in e.g. JS: https://github.com/mxschmitt/playwright-test-coverage.

Folding into microsoft/playwright#9208.