docs: fix import issues with jest-dom (testing-library#913)

Author: sidharthv96

docs/dom-testing-library/example-intro.mdx

@@ -17,7 +17,7 @@ import {
   waitFor,
 } from '@testing-library/dom'
 // adds special assertions like toHaveTextContent
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 
 function getExampleDOM() {
   // This is just a raw example of setting up some DOM

docs/ecosystem-user-event.mdx

@@ -444,7 +444,7 @@ Options:
 ```jsx
 import React from 'react'
 import {render, screen} from '@testing-library/react'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 import userEvent from '@testing-library/user-event'
 
 it('should cycle elements in document tab order', () => {

docs/example-reach-router.mdx

@@ -13,7 +13,7 @@ import {
   createMemorySource,
   LocationProvider,
 } from '@reach/router'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 
 const About = () => <div>You are on the about page</div>
 const Home = () => <div>You are home</div>

docs/example-react-context.mdx

@@ -6,7 +6,7 @@ title: React Context
 ```jsx
 import React from 'react'
 import {render, screen} from '@testing-library/react'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 import {NameContext, NameProvider, NameConsumer} from '../react-context'
 
 /**

docs/example-react-intl.mdx

@@ -103,7 +103,7 @@ export {render}
 
 ```jsx
 import React from 'react'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 // We're importing from our own created test-utils and not RTL's
 import {render, screen, setupTests} from '../test-utils.js'
 import {FormattedDate} from 'react-intl'

docs/example-react-router.mdx

@@ -51,7 +51,7 @@ import {createMemoryHistory} from 'history'
 import React from 'react'
 import {Router} from 'react-router-dom'
 
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 
 import {App, LocationDisplay} from './app'
 

docs/guide-disappearance.mdx

@@ -97,7 +97,7 @@ in the body of the document, or not. This can be more meaningful than asserting
 a query result is `null`.
 
 ```javascript
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 // use `queryBy` to avoid throwing an error with `getBy`
 const submitButton = screen.queryByText('submit')
 expect(submitButton).not.toBeInTheDocument()

docs/preact-testing-library/example.mdx

@@ -32,7 +32,7 @@ function HiddenMessage({children}) {
 
 ```jsx
 // NOTE: jest-dom adds handy assertions to Jest and it is recommended, but not required.
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 
 import {h} from 'preact'
 import {render, fireEvent} from '@testing-library/preact'

docs/react-testing-library/api.mdx

@@ -47,7 +47,7 @@ render(<div />)
 
 ```jsx
 import {render} from '@testing-library/react'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 
 test('renders a message', () => {
   const {container, getByText} = render(<Greeting />)

docs/react-testing-library/example-intro.mdx

@@ -14,7 +14,7 @@ import React from 'react'
 import {rest} from 'msw'
 import {setupServer} from 'msw/node'
 import {render, fireEvent, waitFor, screen} from '@testing-library/react'
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 import Fetch from '../fetch'
 
 const server = setupServer(
@@ -78,7 +78,7 @@ import {setupServer} from 'msw/node'
 import {render, fireEvent, waitFor, screen} from '@testing-library/react'
 
 // add custom jest matchers from jest-dom
-import '@testing-library/jest-dom/extend-expect'
+import '@testing-library/jest-dom'
 // the component to test
 import Fetch from '../fetch'
 ```