Update fetch documentation about polyfills

Author: Timer

packages/react-scripts/template/README.md

@@ -998,11 +998,14 @@ Create React App will add decorator support when the specification advances to a
 
 ## Fetching Data with AJAX Requests
 
-React doesn't prescribe a specific approach to data fetching, but people commonly use either a library like [axios](https://github.com/axios/axios) or the [`fetch()` API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) provided by the browser. Conveniently, Create React App includes a polyfill for `fetch()` so you can use it without worrying about the browser support.
+React doesn't prescribe a specific approach to data fetching, but people commonly use either a library like [axios](https://github.com/axios/axios) or the [`fetch()` API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) provided by the browser.
 
 The global `fetch` function allows you to easily make AJAX requests. It takes in a URL as an input and returns a `Promise` that resolves to a `Response` object. You can find more information about `fetch` [here](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch).
 
-This project also includes a [Promise polyfill](https://github.com/then/promise) which provides a full implementation of Promises/A+. A Promise represents the eventual result of an asynchronous operation, you can find more information about Promises [here](https://www.promisejs.org/) and [here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise). Both axios and `fetch()` use Promises under the hood. You can also use the [`async / await`](https://davidwalsh.name/async-await) syntax to reduce the callback nesting.
+A Promise represents the eventual result of an asynchronous operation, you can find more information about Promises [here](https://www.promisejs.org/) and [here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise). Both axios and `fetch()` use Promises under the hood. You can also use the [`async / await`](https://davidwalsh.name/async-await) syntax to reduce the callback nesting.
+
+Make sure the [`fetch()` API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) and [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) are available in your target audience's browsers.
+For example, support in Internet Explorer requires a [polyfill](https://github.com/facebook/create-react-app/blob/next/packages/react-app-polyfill/README.md).
 
 You can learn more about making AJAX requests from React components in [the FAQ entry on the React website](https://reactjs.org/docs/faq-ajax.html).