Testing in webpack workflow

Hello contributors,

The plugin is test covered as unit library.
We should add test in a webpack workflow.

## Contribution

- Creation of a demo webpack build (1 html file, 1 css file)
- Use of this [plugin](https://github.com/iGitScor/webpack-filesystem-plugin)
- Test the webpack build (_the plugin result_)

## Tests

- [ ] cp command
- [ ] rm command