Reorder installation sections and add to readme for consistency (#433)

* Move template up in installation instructions

Ported from recent changes in reduxjs/react-redux#1543

* Fix heading levels for accessibility

* Don't assume React is used in installation

* Add installation to readme

Author: nickserv

README.md

@@ -7,11 +7,34 @@
 
 **The official, opinionated, batteries-included toolset for efficient Redux development**
 
-`npm install @reduxjs/toolkit`
-
 (Formerly known as "Redux Starter Kit")
 
-### Purpose
+## Installation
+
+### Using Create React App
+
+The recommended way to start new apps with React and Redux Toolkit is by using the [official Redux+JS template](https://github.com/reduxjs/cra-template-redux) for [Create React App](https://github.com/facebook/create-react-app), which takes advantage of React Redux's integration with React components.
+
+```sh
+npx create-react-app my-app --template redux
+```
+
+### An Existing App
+
+Redux Toolkit is available as a package on NPM for use with a module bundler or in a Node application:
+
+```bash
+# NPM
+npm install @reduxjs/toolkit
+
+# Yarn
+yarn add @reduxjs/toolkit
+```
+
+It is also available as a precompiled UMD package that defines a `window.RTK` global variable.
+The UMD package can be used as a [`<script>` tag](https://unpkg.com/@reduxjs/toolkit/dist/redux-toolkit.umd.js) directly.
+
+## Purpose
 
 The **Redux Toolkit** package is intended to be the standard way to write Redux logic. It was originally created to help address three common concerns about Redux:
 
@@ -23,7 +46,7 @@ We can't solve every use case, but in the spirit of [`create-react-app`](https:/
 
 This package is _not_ intended to solve every possible use case for Redux, and is deliberately limited in scope. It does _not_ address concepts like "reusable encapsulated Redux modules", data fetching, folder or file structures, managing entity relationships in the store, and so on.
 
-### What's Included
+## What's Included
 
 Redux Toolkit includes:
 

docs/introduction/quick-start.md

@@ -35,6 +35,16 @@ Redux Toolkit includes:
 
 ## Installation
 
+### Using Create React App
+
+The recommended way to start new apps with React and Redux Toolkit is by using the [official Redux+JS template](https://github.com/reduxjs/cra-template-redux) for [Create React App](https://github.com/facebook/create-react-app), which takes advantage of React Redux's integration with React components.
+
+```sh
+npx create-react-app my-app --template redux
+```
+
+### An Existing App
+
 Redux Toolkit is available as a package on NPM for use with a module bundler or in a Node application:
 
 ```bash
@@ -48,14 +58,6 @@ yarn add @reduxjs/toolkit
 It is also available as a precompiled UMD package that defines a `window.RTK` global variable.
 The UMD package can be used as a [`<script>` tag](https://unpkg.com/@reduxjs/toolkit/dist/redux-toolkit.umd.js) directly.
 
-## Create a React Redux App
-
-The recommended way to start new apps with React and Redux Toolkit is by using the [official Redux+JS template](https://github.com/reduxjs/cra-template-redux) for [Create React App](https://github.com/facebook/create-react-app), which takes advantage of React Redux's integration with React components.
-
-```sh
-npx create-react-app my-app --template redux
-```
-
 ## Help and Discussion
 
 The **[#redux channel](https://discord.gg/0ZcbPKXt5bZ6au5t)** of the **[Reactiflux Discord community](http://www.reactiflux.com)** is our official resource for all questions related to learning and using Redux. Reactiflux is a great place to hang out, ask questions, and learn - come join us!