Add a React Native alias, and one to start the web server (#5711)

* Add a React Native alias, and one to start the web server

* Reorganise aliases in react-native plugin

* Update README for react-native plugin:

  Fix format and add a brief description
  Add missing aliases in react-native plugin README

plugins/react-native/README.md

-# React Native 
+# React Native plugin
 
-**Maintainer:** [BilalBudhani](https://github.com/BilalBudhani)
+This plugin adds completion for [`react-native`](https://facebook.github.io/react-native/).
+It also defines a few [aliases](#aliases) for the commands more frequently used.
 
-### List of Aliases
+To enable, add `react-native` to your `plugins` array in your zshrc file:
 
-Alias | React Native command
-------|---------------------
-**rnand** | *react-native run-android*
-**rnios** | *react-native run-ios*
-**rnios4s** | *react-native run-ios --simulator "iPhone 4s"*
-**rnios5** | *react-native run-ios --simulator "iPhone 5"*
-**rnios5s** | *react-native run-ios --simulator "iPhone 5s"*
+```zsh
+plugins=(... react-native)
+```
 
+## Aliases
+
+| Alias       | React Native command                           |
+|:------------|:-----------------------------------------------|
+| **rn**      | `react-native`                                 |
+| **rns**     | `react-native start`                           |
+| **rnlink**  | `react-native link`                            |
+| _App testing_                                                |
+| **rnand**   | `react-native run-android`                     |
+| **rnios**   | `react-native run-ios`                         |
+| **rnios4s** | `react-native run-ios --simulator "iPhone 4s"` |
+| **rnios5**  | `react-native run-ios --simulator "iPhone 5"`  |
+| **rnios5s** | `react-native run-ios --simulator "iPhone 5s"` |
+| **rnios6**  | `react-native run-ios --simulator "iPhone 6"`  |
+| **rnios6s** | `react-native run-ios --simulator "iPhone 6s"` |

plugins/react-native/react-native.plugin.zsh

+alias rn='react-native'
+alias rns='react-native start'
+alias rnlink='react-native link'
+
 alias rnand='react-native run-android'
+alias rnios='react-native run-ios'
 alias rnios4s='react-native run-ios --simulator "iPhone 4s"'
 alias rnios5='react-native run-ios --simulator "iPhone 5"'
 alias rnios5s='react-native run-ios --simulator "iPhone 5s"'
 alias rnios6='react-native run-ios --simulator "iPhone 6"'
 alias rnios6s='react-native run-ios --simulator "iPhone 6s"'
-alias rnios='react-native run-ios'
-alias rnlink='react-native link'
-