Expose the NuxtPage interface for improved type safety in E2E tests

[sir-kain]

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Export the NuxtPage interface for improved type safety in E2E tests

The NuxtPage interface provides extended typing for Playwright's Page object. However, this interface is not exported in the current implementation, making it inaccessible for users.

Example of usage:

import type { NuxtPage } from '@nuxt/test-utils'

const testPageFunction = async (page: NuxtPage) => {
  const heading = await page.getByRole('heading');
  expect(await heading.isVisible()).toBe(true);
};