Global custom query setup example breaks screen

[bogden1]

The setup example for adding custom queries globally for (at least) React seems to break screen-specific functionality such as screen.debug().

If I understand correctly (via testing-library/dom-testing-library#516 (comment)) this bit:

const customScreen = within(document.body, allQueries)

should be something like this:

const customScreen = { ...screen, ...within(document.body, allQueries) };

And of course that means you have to import screen, too.