Updated also node in docs and centos install script

Author: DmitriyStoyanov

centos_install.sh

@@ -27,7 +27,7 @@ until python3 -m pip install --user -r .github/workflows/requirements.txt
 do
     sleep 1
 done
-curl --silent --location https://rpm.nodesource.com/setup_16.x | sudo bash -
+curl --silent --location https://rpm.nodesource.com/setup_18.x | sudo bash -
 until sudo yum -y install nodejs
 do
     sleep 1

docs/install.md

@@ -47,7 +47,7 @@ wptagent currently supports Windows, Linux and OSX for desktop browsers as well
 ## For lighthouse testing
 * NodeJS
     * Ubuntu/Debian:
-        * ```curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -```
+        * ```curl -sL https://deb.nodesource.com/setup_18.x | sudo -E bash -```
         * ```sudo apt-get install -y nodejs```
 * The lighthouse npm module
     * ```sudo npm install -g lighthouse```