Support for getLocalIdent

[micantoine]

Add option to generate custom classname, issue #6

...
 preprocess: [
   cssModules({
     getLocalIdent: (
       { context, resourcePath }, // context
       { template, interpolatedName }, // localIdentName
       className, // css classname
       { markup, style } // content
     ) => {
       return 'whatever-classname';
     }
   })
 ],
...

Example

# Directory
SvelteApp
└─ src
   ├─ App.svelte
   └─ components
      └─ Button.svelte

<!-- Button.svelte -->
<script>
  export let label = 'Send';
</script>

<button class="$style.red">{label}</button>

<style>
  .red { background-color: red; }
</style>

// Preprocess config
...
 preprocess: [
   cssModules({
     localIdentName: '[path][name]__[local]',
     getLocalIdent: (
       { context, resourcePath }, localIdentName, className, { style }
     ) => {
       console.log(context); // SvelteApp/src/components
       console.log(resourcePath); // SvelteApp/src/components/Button.svelte

       console.log(localIdentName);
       // {
       //    template: '[path][name]__[local]',
       //    interpolatedName: 'SvelteApp_src_components_Button__red',
       // } 

       console.log(className); // red
       console.log(style); // <style>.red { background-color: red; }</style>
       
       const customClass = localIdentName.interpolatedName.toLowerCase().replace('src_', '');
       return customClass; // svelteapp_components_button__red;
     }
   })
 ],
...