addEntries(entries) {
        webpackConfig.addEntries(entries);

        return this;
    }
Adds a collection of JavaScript files that should be webpacked:

```
// final output file will be main.js in the output directory
Encore.addEntries({
  main: './path/to/some_file.js',
  secondary: './path/to/another_file.js',
});
```

If the JavaScript files imports/requires CSS/Sass/LESS files,
then a CSS file (e.g. main.css) will also be output.

@param {Record<string, string|string[]>} entries where the Keys are the
                           names (without extension) that will be used
                           as the output filename (e.g. app will become app.js)
                           in the output directory. The values are the path(s)
                           to the source file(s).
@returns {Encore}