Fix outdated Nodejs version and the steps for how to create a new sub theme

Problem/Motivation

The documentation page is outdated for the "Create a Vartheme BS4 sub theme ( Bootstrap 4 ) SASS for a project"
https://github.com/Vardot/vartheme_bs4/blob/9.0.5/scripts/README.md

Proposed resolution

• Update the documentation page for "Creating Your Own Theme"
• Require to use Nodejs 14 and more
• Have a new bash command to Install Needed Tools

cd PROJECT_DIR_NAME/docroot/themes/contrib/vartheme_bs4/scripts
bash ./install-needed-tools.sh

Have a better and clean steps to Install Needed Tools Manually

Have that updated at the 9.0.x branch
https://github.com/Vardot/vartheme_bs4/blob/9.0.x/scripts/README.md
The the 9.0.6 release
https://github.com/Vardot/vartheme_bs4/blob/9.0.6/scripts/README.md

Have a follow up update for the README.md in the Varbase profile's scripts folder too