update npm on centos code example

Example 1: update nodejs centos

$ curl -sL https://rpm.nodesource.com/setup_12.x | bash -
sudo yum install nodejs

Example 2: How to install npm in centos

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
source ~/.bash_profile
nvm list-remote