entry.js

import 'bootstrap/dist/css/bootstrap.css'
import 'bootstrap-vue/dist/bootstrap-vue.css'

// JS import
import Vue from 'vue';
import App from './App.vue'
import BootstrapVue from 'bootstrap-vue'

Vue.use(BootstrapVue);

new Vue({
  el: '#app',
  render: h => h(App)
})

main.js

const { app, BrowserWindow } = require("electron");

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the JavaScript object is garbage collected.
let win;

function createWindow() {
  // Create the browser window.
  win = new BrowserWindow({ width: 800, height: 600 });

  // and load the index.html of the app.
  win.loadFile("index.html");

  // Open the DevTools.
  win.webContents.openDevTools();

  // Emitted when the window is closed.
  win.on("closed", () => {
    // Dereference the window object, usually you would store windows
    // in an array if your app supports multi windows, this is the time
    // when you should delete the corresponding element.
    win = null;
  });
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.on("ready", createWindow);

// Quit when all windows are closed.
app.on("window-all-closed", () => {
  // On macOS it is common for applications and their menu bar
  // to stay active until the user quits explicitly with Cmd + Q
  if (process.platform !== "darwin") {
    app.quit();
  }
});

app.on("activate", () => {
  // On macOS it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (win === null) {
    createWindow();
  }
});

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

package.json

{
  "name": "tool",
  "version": "1.0.0",
  "main": "main.js",
  "scripts": {
    "dev": "webpack",
    "start": "electron ."
  },
  "license": "MIT",
  "private": true,
  "dependencies": {
    "bootstrap-vue": "^2.0.0-rc.11"
  },
  "devDependencies": {
    "css-loader": "^0.25.0",
    "electron": "^1.4.3",
    "electron-reload": "^1.0.2",
    "extract-text-webpack-plugin": "^3.0.2",
    "file-loader": "^0.9.0",
    "jquery": "^3.3.1",
    "postcss-base64": "^0.7.1",
    "postcss-cssnext": "^3.1.0",
    "postcss-import": "^11.1.0",
    "postcss-loader": "^2.1.5",
    "postcss-smart-import": "^0.7.6",
    "postcss-url": "^7.3.2",
    "style-loader": "^0.21.0",
    "vue": "^2.5.16",
    "vue-loader": "^9.5.1",
    "webpack": "^3.4.1"
  }
}

webpack.config.js

var path = require("path");
var ExtractTextPlugin = require("extract-text-webpack-plugin");

module.exports = {
  watch: true,
  target: "electron",
  entry: "./app/src/entry.js",
  output: {
    path: __dirname + "/app/build",
    publicPath: "build/",
    filename: "bundle.js"
  },

  module: {
    loaders: [
      {
        test: /\.css$/,
        loader: ExtractTextPlugin.extract({
          fallback: "style-loader",
          use: [
            {
              loader: "css-loader",
              options: { importLoaders: 1 }
            }
          ]
        })
      },
      {
        test: /\.vue$/,
        loader: "vue-loader"
      },
      {
        test: /\.(png|jpg|gif|svg)$/,
        loader: "file-loader",
        query: {
          name: "[name].[ext]?[hash]"
        }
      },
      {
        test: /\.(ttf|eot|svg|woff(2)?)(\?[a-z0-9=&.]+)?$/,
        use: ["file-loader"]
      }
    ]
  },
  resolve: {
    alias: { vue: "vue/dist/vue.js" }
  },
  plugins: [new ExtractTextPlugin("[name].css")]
};