title: nodejs react : build script in package.json file not working when commanding yarn build
body: <p>Both on linux and windows when I run the yarn build command after making the following edits on package.json:</p>
  
  <pre><code>{  
  "name": "chatastrophe",  
  "version": "1.0.0", 
   "main": "index.js",
    "license": "MIT", 
   "scripts": {  
    "build": "node_modules/.bin/webpack",
  '  }, 
   "dependencies": {   
   "react": "15.6.1",  
    "react-dom": "15.6.1", 
     "webpack": "3.5.4",
    } 
  }
  </code></pre>
  
  <p>I keep getting this error:</p>
  
  <blockquote>
    <p>error An unexpected error occurred:
    "C:\Users\Richard\Desktop\chatastrophe\package.json: Unexpected
    token } in JSON at position 175". info If you think this is a bug,
    please open a bug report with the information provided in
    "C:\Users\Richard\Desktop\chatastrophe\yarn-error.log".</p>
  </blockquote>
  
  <p>a more detailed version of this error is as follows (when I use npm instead of yarn)</p>
  
  <pre><code>npm ERR! file C:\Users\Richard\Desktop\chatastrophe\package.json
  npm ERR! code EJSONPARSE
  npm ERR! Failed to parse json
  npm ERR! Unexpected token } in JSON at position 175 while parsing near '...webpack",
  npm ERR!           },
  npm ERR!         "dependen...'
  npm ERR! File: C:\Users\Richard\Desktop\chatastrophe\package.json
  npm ERR! Failed to parse package.json data.
  npm ERR! package.json must be actual JSON, not just JavaScript.
  npm ERR!
  npm ERR! Tell the package author to fix their package.json file. JSON.parse
  </code></pre>
  
  <p>can anyone please help me out. Thanks in advance.</p>