upgrade reactjs version code example

Example: update react version

//Is used to update the version only; such as 16.0.0 can be update to latest 16.13.0 but.. 
//but.. 15.0.0 can't be updated to 16.13.0 or to 16.0.0 with this
npm update react

//Use this to go from 15.0.0 to 16.13.0
npm install --save react@latest