webpack.config.js

// webpack.config.js

"use strict";

const path = require("path");
const { styles } = require("@ckeditor/ckeditor5-dev-utils");

module.exports = {
  // https://webpack.js.org/configuration/entry-context/
  entry: "./app.js",

  // https://webpack.js.org/configuration/output/
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "bundle.js",
  },

  module: {
    rules: [
      {
        test: /ckeditor5-[^/\\]+[/\\]theme[/\\].+\.css$/,

        use: [
          {
            loader: "style-loader",
            options: {
              injectType: "singletonStyleTag",
              attributes: {
                "data-cke": true,
              },
            },
          },
          "css-loader",
          {
            loader: "postcss-loader",
            options: {
              postcssOptions: styles.getPostCssConfig({
                themeImporter: {
                  themePath: require.resolve("@ckeditor/ckeditor5-theme-lark"),
                },
                minify: true,
              }),
            },
          },
        ],
      },
    ],
  },

  // Useful for debugging.
  devtool: "source-map",

  // By default webpack logs warnings if the bundle is bigger than 200kb.
  performance: { hints: false },
};