How can I make middleman work with custom fonts & font-awesome through webpack?

Question

I'm using middleman with webpack. Thus my config.rb contains this configuration for an external pipeline (webpack):

activate :external_pipeline,
         name: :webpack,
         command: build? ? 'yarn run build' : 'yarn run start',
         source: '.tmp/dist',
         latency: 1

and package.json contains this:

  "scripts": {
    "build": "webpack --bail -p --config webpack.config.js",
    "start": "webpack --watch --progress --color --config webpack.config.js"
  },

This is how the webpack.config.js looks like

// webpack.config.js

var path = require('path');
var webpack = require('webpack');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  mode: 'development',
  entry: {
    application: './source/javascripts/application.js',
    styles: './source/stylesheets/application.scss',
  },
  output: {
    path: __dirname + '/.tmp/dist',
    filename: '[name].js',
  },
  module: {
    rules: [
      {
        test: /\.s[ac]ss$/i,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[name].css'
            }
          },
          {
            loader: 'sass-loader',
            options: {
              sourceMap: true
            }
          }
        ],
      },
      {
        test: /\.css$/,
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              hmr: process.env.NODE_ENV === 'development',
            },
          },
          'css-loader',
          'postcss-loader',
        ]
      },
      {
        test: /\.(png|svg|jpg|jpeg|gif)$/,
        use: [
          'file-loader',
        ],
      },
      {
        test: /\.(woff(2)?|ttf|eot|svg|otf)(\?v=[0-9]\.[0-9]\.[0-9])?$/,
        loader: 'file-loader',
        options: {
          name: 'fonts/[name].[ext]?[hash]'
        }
      }
    ]
  }
}

The page uses some custom fonts already (located in source/fonts) but now I also want to use Font Awesome through webpack. But somehow I'm unable to get it work, without copying the fonts manually from the font awesome font directory to source/fonts folder. I'm sure it is related to the webpack.config.js but I can't figure out, how I have to integrate it.

Although I'm not sure whether it's relevant — this is how I included the SCSS:

// source/stylesheets/application.scsss
@charset "utf-8";

@import "../../node_modules/@fortawesome/fontawesome-free/scss/fontawesome.scss";
@import "../../node_modules/@fortawesome/fontawesome-free/scss/regular.scss";

PS: Just to clarify this. I want to use webpack to have all assets handled in one place (webpack). Therefore I don't have any interest in using font-awesome-middleman or similar gems.