Improve readme

Author: joernb

README.md

@@ -3,4 +3,66 @@
 [![Build Status](https://travis-ci.org/joernb/react-scripts-with-ssr.svg?branch=master)](https://travis-ci.org/joernb/react-scripts-with-ssr)
 
 This is a fork of [react-scripts](https://github.com/facebook/create-react-app/tree/master/packages/react-scripts), which adds support for server-side rendering (SSR).
-react-scripts is a part of [Create React App](https://github.com/facebook/create-react-app), which can be used with a customized version of react-scripts.
+
+`react-scripts` is a part of [Create React App](https://github.com/facebook/create-react-app), which can be used with a customized version of `react-scripts`.
+
+## Getting Started
+
+Install create-react-app:
+```sh
+npm i -g create-react-app
+```
+
+Generate a new project (add `--typescript` for TypeScript support):
+```sh
+npx create-react-app my-app --scripts-version react-scripts-with-ssr
+cd my-app
+```
+
+Start a local webpack dev server with integrated server-side rendering:
+```sh
+npm start
+```
+
+Build a production version and test server-side rendering locally:
+```sh
+npm run build
+npm run serve
+```
+
+## How it works
+
+The script will generate an additional entry point for server-side rendering in `src/index.ssr.js` (or `src/index.ssr.tsx`). It exports an express-style request handler, that looks like this:
+
+```js
+export default (request, response) => {
+  // ...
+  response.status(200).send("...");
+};
+```
+
+Webpack will compile this entry point as a separate library `build/ssr.js`. In production, that library may be imported by an executable node script, which sets up an express server and plugs in the request handler. Such a script is provided as an example at `react-scripts-with-ssr/scripts/serve.js`, which you may start with `npm run serve` to test your production builds. That script however is not part of the compilation. It is up to you to integrate the request handler into your server-side runtime environment.
+
+During development, the request handler will be integrated into the local webpack dev server. Start it with `npm start` and open `http://localhost:3000` to see the server-side rendered output.
+
+If `src/index.ssr.js` exports a function called `devServerHandler`, it will be invoked and its return value will be used as a request handler during development instead. This gives your entry point the possibility to make environment-specific adjustments. For example, all assets are compiled in-memory during development and should not be served from the real file system.
+
+## Contribute
+
+### Merge react-scripts updates
+
+Clone create-react-app and create a subtree branch for react-scripts:
+
+```sh
+git clone git@github.com:facebook/create-react-app.git create-react-app
+cd create-react-app
+git checkout react-scripts@2.1.3
+git subtree split -P packages/react-scripts -b react-scripts-v2.1.3
+```
+
+Merge the subtree branch into this project:
+
+```sh
+git remote add upstream ../create-react-app
+git merge upstream react-scripts-v2.1.3
+```