Make sure you have latest Ruby, then make sure you have the bundler:

gem install bundler

You will also need PlantUML to build the docs

Finally you can install requirements:

# from the root of this project
cd docs
bundle install

To link the build directory to the gh-pages branch, ensure the docs/_site directory does NOT exists and run:

npm run doc:link

To preview your changes with live-reload, run this:

npm run doc