Add missing '\n' to the end of package.json file (facebook#1510)

Author: pd4d10

packages/react-scripts/scripts/eject.js

@@ -145,7 +145,7 @@ prompt(
 
   fs.writeFileSync(
     path.join(appPath, 'package.json'),
-    JSON.stringify(appPackage, null, 2)
+    JSON.stringify(appPackage, null, 2) + '\n'
   );
   console.log();