Add clarifying note to TypeScript docs warning about global install of CRA (#6945)

Added block quote with warning about issues when CRA is installed globally.

Author: methodbox

docusaurus/docs/adding-typescript.md

@@ -17,6 +17,8 @@ npx create-react-app my-app --typescript
 yarn create react-app my-app --typescript
 ```
 
+> If you've previously installed `create-react-app` globally via `npm install -g create-react-app`, we recommend you uninstall the package using `npm uninstall -g create-react-app` to ensure that `npx` always uses the latest version.
+
 To add [TypeScript](https://www.typescriptlang.org/) to a Create React App project, first install it:
 
 ```sh