Add docs for creating new TypeScript project (#6015)

Author: mbelsky

docusaurus/docs/adding-typescript.md

@@ -7,6 +7,14 @@ title: Adding TypeScript
 
 [TypeScript](https://www.typescriptlang.org/) is a typed superset of JavaScript that compiles to plain JavaScript.
 
+To start a new Create React App project with [TypeScript](https://www.typescriptlang.org/), you can run:
+
+```bash
+$ npx create-react-app my-app --typescript
+$ # or
+$ yarn create react-app my-app --typescript
+```
+
 To add [TypeScript](https://www.typescriptlang.org/) to a Create React App project, first install it:
 
 ```bash