##Installation composer require twin-elements/form-extensions

in /config/packages/routes.yaml

filemanager_image:
    resource: "@TwinElementsFormExtensionsBundle/Controller/FileManagerImageController.php"
    prefix: /admin
    type: annotation
    requirements:
        _locale: '%app_locales%'
    defaults:
        _locale: '%locale%'
        _admin_locale: '%admin_locale%'
    options: { i18n: false }

in assets/admin/cropper.js add

import 'twin-elements/forms/resources/image-cropper-js';

in webpack.config.js

add const twinElementsFormScripts = path.resolve(__dirname, 'vendor/twin-elements/form-extensions/src/Resources/private/')

add .addEntry('cropper', './assets/admin/cropper.js') to admin config in webpack.config.js

add path aliases to admin config

adminConfig.resolve.alias['twin-elements/forms/resources'] = twinElementsFormScripts;
adminConfig.resolve.alias['root-dir'] = rootDir;