We created a custom Bootstrap 4 style & templates to ensure all frontends had consistent UI functionality. Our starter kit includes all the templates & info required to get up and running.
Instead of having the Bootstrap theme included locally, we recommend loading the precompiled theme from our CDN (our header template does this by default):
<link rel="stylesheet" href="//demo.productionready.io/main.css" />
Alternatively, if you want to make modifications to the theme, check out the theme's repo.