[userEvent/fireEvent]: fireEvent docs say to use userEvent, but all React code samples use fireEvent

Description:

Hey there 👋 - our team is newer to testing-library/react, and just had a bit of confusion in PR review whereby we went back and forth on whether to use fireEvent or userEvent.

All of the code examples in the react documentation:

https://testing-library.com/docs/react-testing-library/example-intro

https://testing-library.com/docs/react-testing-library/api/#asfragment

https://testing-library.com/docs/react-testing-library/cheatsheet/

use fireEvent, but then my colleague saw this:

from the core API https://testing-library.com/docs/dom-testing-library/api-events

We're wondering if maybe some of the code examples in the React documentation should use userEvent, given that the API docs for fireEvent give an impression that userEvent is more useful in most projects.

Thanks!

To Reproduce:

1. Observe all code samples in https://testing-library.com/docs/react-testing-library/intro use fireEvent
2. Observe fireEvent API documentation recommends userEvent

Expected behavior:

The userEvent API is present in React code samples

Screenshots:

N/A

Desktop:

N/A

Smartphone:

N/A

Review the React documentation examples linked in the issue, including the example intro, API/AsFragment page, cheatsheet, and intro, alongside the DOM Testing Library fireEvent guidance. Update the relevant examples so the relationship between fireEvent and userEvent is consistent and clear, then verify the documentation examples show the expected userEvent API usage.