[Docs]: Improve documentation for metadata

[vitalets]

Page(s)

https://playwright.dev/docs/next/api/class-testconfig#test-config-metadata

Description

1. Current metadata example does not pass TypeScript check:

import { defineConfig } from '@playwright/test';

export default defineConfig({
  metadata: 'acceptance tests',
});

Result:

Type 'string' is not assignable to type 'Metadata'.

2. Documentation should mention the certain fields that are allowed in metadata, e.g.

export type Metainfo = {
  'revision.id'?: string;
  'revision.author'?: string;
  'revision.email'?: string;
  'revision.subject'?: string;
  'revision.timestamp'?: number | Date;
  'revision.link'?: string;
  'ci.link'?: string;
  'timestamp'?: number
};

[dgozman]

We discussed this issue, and are not sure how to improve it.