To work on the website and see changes live as you save, run:
node_modules/.bin/gulp serve
That command will build the site and start a local server. To work on only the website without the docs, add the --nodocs flag, as follows:
node_modules/.bin/gulp serve --nodocs
Alternatively, to dynamically rebuild the site and refresh the browser when changes happen (again, optionally with the --nodocs flag), run:
node_modules/.bin/gulp watch