craco.config.js

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

module.exports = {
    webpack: {
        configure: (config, { env, paths }) => {
            config.plugins.push(
                new CKEditorWebpackPlugin({
                    language: "en",
                    addMainLanguageTranslationsToAllAssets: true,
                }),
            );

            const regExpThemeIconSvg =
                /ckeditor5-[^/\\]+[/\\]theme[/\\]icons[/\\][^/\\]+\.svg$/;
            const regExpThemeCss = /ckeditor5-[^/\\]+[/\\]theme[/\\].+\.css/;
            const cssRegex = /\.css$/;
            const cssModuleRegex = /\.module\.css$/;
            config.module.rules.push(
                { test: regExpThemeIconSvg, use: ["raw-loader"] },
                {
                    test: regExpThemeCss,
                    use: [
                        {
                            loader: "style-loader",
                            //   options: { injectType: "singletonStyleTag" }
                        },
                        {
                            loader: "postcss-loader",
                            options: styles.getPostCssConfig({
                                themeImporter: {
                                    themePath: require.resolve(
                                        "@ckeditor/ckeditor5-theme-lark",
                                    ),
                                },
                                minify: true,
                            }),
                        },
                    ],
                },
            );

            config.module.rules.forEach(rule => {
                if (rule.oneOf) {
                    rule.oneOf.forEach(subRule => {
                        if (String(subRule.test) === String(cssRegex)) {
                            subRule.exclude = [cssModuleRegex, regExpThemeCss];
                        }

                        if (String(subRule.test) === String(cssModuleRegex)) {
                            subRule.exclude = [regExpThemeCss];
                        }

                        if (
                            String(subRule.loader).includes("file-loader") &&
                            Array.isArray(subRule.exclude)
                        ) {
                            subRule.exclude.push(
                                regExpThemeIconSvg,
                                regExpThemeCss,
                            );
                        }
                    });
                }
            });

            return config;
        },
    },
};