Webpack-2 externals how to load bootstrap from cdn

I created my webpack config file and it works fine. I want to use externals to load some libs from CDN:

externals:{
        jQuery: 'jquery',
        $: 'jquery',
        moment: "moment",
        Highcharts:'highcharts',
        tether: 'tether',
        Tether: 'tether',
        'window.Tether': 'tether'
        }

Still I cannot load bootstrap. I tried bootstrap:'bootstrap' bootstrap:true but it doesn't work. I tried import and require in my file. When i require jquery var $ = require('../../../node_modules/jquery/dist/jquery'); bootstrap modal gets error, and when I comment out require jquery I see a jquery error.

For now I have no idea how to solve this.