Add standalone Playwright Trace Viewer

Idea came while using `playwright-bdd/reporter/cucumber` from `playwright-bdd` package
```ts
reporter: [
cucumberReporter('html', {
outputFile: 'cucumber-report/index.html',
externalAttachments: true,
})
]
```

Start with the playwright-bdd cucumber reporter example in the issue and inspect the generated HTML and external attachments. Clarify which Playwright trace artifacts the standalone viewer must open and how it should be included in the Allure report; done means the agreed trace-viewing flow works with that configuration.

Written by the indexing model from the issue text.