This Bundle provide the Symfony Webpack Encore for Contao.
It is preconfigured for the webpack encore extension. If you use own things, so overwrite it in your project.
The pre configuration for the extension is:
webpack_encore:
output_path: '%kernel.project_dir%/web/layout'
How to use Webpack Encore can you read here .
In Contao you can add your sources in the page layout.