Install packages below. You can use npm or yarn.

yarn add primer-css
yarn add sass-loader node-sass --dev

We use Vue.js official webpack biolerplate as example, edit build/utils. Add node_modules to include paths for style loader option.

function generateLoaders (loader, loaderOptions) {
  var loaders = [cssLoader]
  if (loader) {
    loaders.push({
      loader: loader + '-loader',
      options: Object.assign({}, loaderOptions, {
      // add this line
      includePaths: [path.join(__dirname, '..', 'node_modules')]

Then import primer-css scss file in your app root component(App.vue in our example project):

<style lang="scss">
@import "primer-css/index.scss";
</style>

That's all.

Alternative solution

Forgive my laziness, as I edit utility function to apply includePaths option to all available loaders directly. For flexibilty, you can edit each build config(like webpack.dev.config.js) and provide includePaths option as arguments.

Change

module: {
  rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap })
},

to

module: {
  rules: utils.styleLoaders({
    sourceMap: config.dev.cssSourceMap,
    includePaths: [path.join(__dirname, '..', 'node_modules')]
  })
},