Deprecate Create React App officially by changing the README, and adding a message on init (facebook#17003)

It's probably time to make this project document its status as being
deprecated and not recommended for production usage.

To change it:

- I opted to add a header to the README saying its over and you should
go look at https://react.dev/learn/start-a-new-react-project

- I left a note saying that if you are following, it is maybe worth
carrying on. While I hear react 19 doesn't work with CRA, I wouldn't be
surprised that a good chunk of tutorials would still work. Open to being
a bit more hard-lined there but there was a lot of great resources for
learning react in that era and it seems like a waste to be making people
stop early?

- I added a message inside the CLI, it shows once and says "don't use
this, use the stuff in
https://react.dev/learn/start-a-new-react-project"

---------

Co-authored-by: Ricky <[email protected]>
Co-authored-by: Rick Hanlon <[email protected]>

Author: 2 people

README.md

@@ -1,4 +1,12 @@
-# Create React App [![Build & Test](https://github.com/facebook/create-react-app/actions/workflows/build-and-test.yml/badge.svg?branch=main)](https://github.com/facebook/create-react-app/actions/workflows/build-and-test.yml) [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-green.svg)](https://github.com/facebook/create-react-app/blob/main/CONTRIBUTING.md)
+## Create React App [![Build & Test](https://github.com/facebook/create-react-app/actions/workflows/build-and-test.yml/badge.svg?branch=main)](https://github.com/facebook/create-react-app/actions/workflows/build-and-test.yml) [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-green.svg)](https://github.com/facebook/create-react-app/blob/main/CONTRIBUTING.md)
+
+> [!CAUTION]
+>
+> ## Deprecated
+>
+> Create React App was one of the key tools for getting a React project up-and-running in 2017-2021, it is now in long-term stasis and we recommend that you migrate to one of React frameworks documented on [Start a New React Project](https://react.dev/learn/start-a-new-react-project).
+>
+> If you are following a tutorial to learn React, there is still value in continuing your tutorial, but we do not recommend starting production apps based on Create React App.
 
 <img alt="Logo" align="right" src="https://create-react-app.dev/img/logo.svg" width="20%" />