brunch-config.js

exports.config = {
 
   ... // Code removed for readability

  // Configure your plugins
  plugins: {
    babel: {
      // Do not use ES6 compiler in vendor code
      ignore: [/web\/static\/vendor/]
    },
    sass: {
      options: {
        includePaths: [
          'node_modules/foundation-sites/scss',
        ]
      }
    }
  },
  
  ... // Code removed for readability
  
};