[Bug]: dist CSS is not mapped in package.json

[Jean85]

Bug description

I'm trying to use this package with the Symfony Asset Mapper, which leverages ESM loading to avoid Node/npm as a requirement. This seems to work well with your package, except for the fact that the CSS dist file is not mapped in the package.json, so ESM does not see that.

Expected behavior

CSS is included in the package, so that CDNs like jsDelivr will consider it and add to the needed files.

Steps to reproduce

1. Go to jsDelivr
2. Click on ESM mode button
3. See that only the JS file is imported:

   <script type="module"> 
   import tomSelect from 'https://cdn.jsdelivr.net/npm/tom-select@2.3.1/+esm'
   </script>

Additional context

The Symfony docs refer to the package.json configuration file as a way to fix this; we probably need to add keys like sass or style to the root of the package.json, like Bootstrap does: https://github.com/twbs/bootstrap/blob/e3e00b5002139adb0d5dadd6002e15b7b6cd371f/package.json#L40