Add README to RN Template App, added when `npx react-native@latest in…

…it <AppName>` (#37521)

Summary:
[skip-ci]
I noticed that; when a _new_ RN App is created using RN CLI there is ***NO*** *README* file added to the project.
Having a simple README file explaining what type of project it is, for example how other web projects do it, such as long lived `create-react-app`, now widely used `create-next-app`, etc.

Why not for React Native App then?

This PR; Adds README file to RN Template App ⚡, which should be added to the project when a new project is created using RN CLI.

### Website PR: facebook/react-native-website#3732 🚀😇

bypass-github-export-checks

## Changelog:

[INTERNAL] [ADDED] - Add README to RN Template App ⚡

Pull Request resolved: facebook/react-native#37521

Test Plan: - The README file should be included in the newly created RN App using RN CLI

Reviewed By: NickGerleman

Differential Revision: D46075719

Pulled By: cipolleschi

fbshipit-source-id: efcccc09d72c57a065b36de6e787594082000e15

Original: facebook/react-native@377a8b7

template/template/README.md

@@ -0,0 +1,79 @@
+This is a new [**React Native**](https://reactnative.dev) project, bootstrapped using [`@react-native-community/cli`](https://github.com/react-native-community/cli).
+
+# Getting Started
+
+>**Note**: Make sure you have completed the [React Native - Environment Setup](https://reactnative.dev/docs/environment-setup) instructions till "Creating a new application" step, before proceeding.
+
+## Step 1: Start the Metro Server
+
+First, you will need to start **Metro**, the JavaScript _bundler_ that ships _with_ React Native.
+
+To start Metro, run the following command from the _root_ of your React Native project:
+
+```bash
+# using npm
+npm start
+
+# OR using Yarn
+yarn start
+```
+
+## Step 2: Start your Application
+
+Let Metro Bundler run in its _own_ terminal. Open a _new_ terminal from the _root_ of your React Native project. Run the following command to start your _Android_ or _iOS_ app:
+
+### For Android
+
+```bash
+# using npm
+npm run android
+
+# OR using Yarn
+yarn android
+```
+
+### For iOS
+
+```bash
+# using npm
+npm run ios
+
+# OR using Yarn
+yarn ios
+```
+
+If everything is set up _correctly_, you should see your new app running in your _Android Emulator_ or _iOS Simulator_ shortly provided you have set up your emulator/simulator correctly.
+
+This is one way to run your app — you can also run it directly from within Android Studio and Xcode respectively.
+
+## Step 3: Modifying your App
+
+Now that you have successfully run the app, let's modify it.
+
+1. Open `App.tsx` in your text editor of choice and edit some lines.
+2. For **Android**: Press the <kbd>R</kbd> key twice or select **"Reload"** from the **Developer Menu** (<kbd>Ctrl</kbd> + <kbd>M</kbd> (on Window and Linux) or <kbd>Cmd ⌘</kbd> + <kbd>M</kbd> (on macOS)) to see your changes!
+
+   For **iOS**: Hit <kbd>Cmd ⌘</kbd> + <kbd>R</kbd> in your iOS Simulator to reload the app and see your changes!
+
+## Congratulations! :tada:
+
+You've successfully run and modified your React Native App. :partying_face:
+
+### Now what?
+
+- If you want to add this new React Native code to an existing application, check out the [Integration guide](https://reactnative.dev/docs/integration-with-existing-apps).
+- If you're curious to learn more about React Native, check out the [Introduction to React Native](https://reactnative.dev/docs/getting-started).
+
+# Troubleshooting
+
+If you can't get this to work, see the [Troubleshooting](https://reactnative.dev/docs/troubleshooting) page.
+
+# Learn More
+
+To learn more about React Native, take a look at the following resources:
+
+- [React Native Website](https://reactnative.dev) - learn more about React Native.
+- [Getting Started](https://reactnative.dev/docs/environment-setup) - an **overview** of React Native and how setup your environment.
+- [Learn the Basics](https://reactnative.dev/docs/getting-started) - a **guided tour** of the React Native **basics**.
+- [Blog](https://reactnative.dev/blog) - read the latest official React Native **Blog** posts.
+- [`@facebook/react-native`](https://github.com/facebook/react-native) - the Open Source; GitHub **repository** for React Native.