Use a top-level .env file to control the internal testing setup.
This allows for easy manipulation of environment variables regardless
of your setup (VSCode Extension, CLI, etc.).
This changes PlaywrigtServer to serve connections like `ws://localhost:3333/?browser=chromium`:
- launches the browser;
- talks `browserType.connect`-style protocol over websocket;
- compatible with `connectOptions` fixture.
```js
await playwright.chromium.connect({ wsEndpoint: 'ws://localhost:3333/?browser=chrome' });
```
