s/npm -g/npx (#1429)

- less invasive
- matches the steps that the link already points to (https://reactjs.org/docs/create-a-new-react-app.html#create-react-app)

content/tutorial/tutorial.md

@@ -77,8 +77,7 @@ This setup requires more work but allows you to complete the tutorial using an e
 2. Follow the [installation instructions for Create React App](/docs/create-a-new-react-app.html#create-react-app) to make a new project.
 
 ```bash
-npm install -g create-react-app
+npx create-react-app my-app
-create-react-app my-app
 ```
 
 3. Delete all files in the `src/` folder of the new project