How to properly include twitter bootstrap in electron app?

This is my first electron app, which is based on quick-start app. I want to add twitter bootstrap's css. So I installed it like this:

npm install bootstrap

And included in the index.html like this:

<link rel="stylesheet" href="node_modules/bootstrap/dist/css/bootstrap.min.css">

When I run: npm start from terminal it works fine. However when I try to build it using electron-packager like this:

npm run build

I get a native mac app "myApp.app", but when I open it, I don't see the styles.

The only files in the application aside from node_modules and package.json are: main.js and index.html and both are in the root dir.

Is there a step here that I am missing?

via Lamar