Using yarn vs npm with typescript docs

When we want to use other TypeScript version and we do:
`npm install [email protected] -D` 
But when we use new features like const casting microsoft/TypeScript#29510 it does not compile.
Instead of that if we use:
`yarn add [email protected]`
Everything works

Author: CKGrafico

docusaurus/docs/adding-typescript.md

@@ -38,6 +38,8 @@ To learn more about TypeScript, check out [its documentation](https://www.typesc
 > **Note:** If your project is not created with TypeScript enabled, npx may be using a cached version of `create-react-app`.
 > Remove previously installed versions with `npm uninstall -g create-react-app` (see [#6119](https://github.com/facebook/create-react-app/issues/6119#issuecomment-451614035)).
 
+> **Note:** If you want to use your own TypeScript version, use yarn instead of npm, otherwise create react app will use internal version.  
+
 > **Note:** You are not required to make a [`tsconfig.json` file](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html), one will be made for you.
 > You are allowed to edit the generated TypeScript configuration.