use yarn to install code example

Example 1: install yarn

npm install -g yarn

Example 2: yarn react install

There are two ways where you can initiate a REACT app.. 
1. Using npm : npm init react-app <app_name>
	 example : npm init react-app sampleApp
2. Using yarn : yarn create react-app <app_name>
	 example : yarn create react-app sampleApp