[dev] CSS hook

[Sebastian Birnbach]

I am working on a whups Block for which I want to use custom CSS
definitions.

I created a whups/themes/default/dossier.css file
I also created a loader function in whups/config/hooks.php:

...
    public function cssfiles($theme)
    {
        return array(
            '/usr/local/www/apache24/data/whups/themes/default/dossier.css'
=>
            'whups/dossier.css'
        );
     }
...

The loader function does get executed no problem but there seems to be a
missing step. How do I use the URI inside the Block to make the CSS file
load? (Sorry if this is a trivial question, I'm still working my way
through the application stack)