docs: move dtl to peerdeps for rtl

Author: MatanBobi

docs/react-testing-library/intro.mdx

@@ -9,19 +9,22 @@ APIs for working with React components.
 
 ## Installation
 
+To get started with `React Testing Library`, you'll need to install it together
+with it's peerDependency `@testing-library/dom`:
+
 ```bash npm2yarn
-npm install --save-dev @testing-library/react
+npm install --save-dev @testing-library/react @testing-library/dom
 ```
 
 ### With TypeScript
 
-To get full type coverage, you need to install the types for `react-dom` as well:
+To get full type coverage, you need to install the types for `react-dom` as
+well:
 
 ```bash npm2yarn
 npm install --save-dev @testing-library/react @types/react-dom
 ```
 
-
 [gh]: https://github.com/testing-library/react-testing-library
 
 ## The problem