Update to React 18+

Author: jpomykala

README.md

@@ -1,11 +1,47 @@
 ## Demo
-[Checkout working demo with 3 languages](https://react-intl.simplelocalize.io)
+[Live demo](https://react-intl.simplelocalize.io)
 
-## Available Scripts
+## Overview
+
+Sample application with 3 languages. The application is built with React 18, react-intl. It uses React Context to keep translation messages
+and FormattedMessage components with **predefined message IDs.** 
+
+```tsx
+<FormattedMessage id="USE_BUTTONS_BELOW" />
+```
+ 
+To **use auto-generated message IDs**, please [eject the app](https://create-react-app.dev/docs/available-scripts/#npm-run-eject)
+ and follow the [Bundling with FormatJS](https://formatjs.io/docs/guides/bundler-plugins/) instructions.
+
+## Built with
+- Create React App
+- React 18+
+- TypeScript 4+
+- React Hooks
+- React Context
+- React Intl - library for internationalization 
+- SimpleLocalize - translation management system
+
+## Extracting translations
+
+In the project directory, you can run:
+### `npm run i18n:extract`
+to extract messages from source code to `lang/en.json` file.
+
+### `npm run i18n:upload`
+to upload messages to the SimpleLocalize service.
+
+### `npm run i18n:download`
+to download messages locally from the SimpleLocalize service. This is optional and it requires to change SimpleLocalize.tsx 
+to load translations from local files.
+
+> Please provide a valid API Key in `simplelocalize.yml` configuration file.
+
+## Running application locally
 
 In the project directory, you can run:
 
-### `yarn start`
+### `npm install && npm start`
 
 Runs the app in the development mode.<br />
 Open [http://localhost:3000](http://localhost:3000) to view it in the browser.