addStyleEntry(name, src) {
        webpackConfig.addStyleEntry(name, src);

        return this;
    }
Adds a CSS/SASS/LESS file that should be webpacked:

```
 // final output file will be main.css in the output directory
 Encore.addStyleEntry('main', './path/to/some_file.css');
```

This is actually not something Webpack does natively, and you
should avoid using this function when possible. A better option
is to use addEntry() and then require/import your CSS files from
within your JavaScript files.

@param {string} name          The name (without extension) that will be used
                              as the output filename (e.g. app will become app.css)
                              in the output directory.
@param {string|string[]} src  The path to the source file (or files)
@returns {Encore}