The callback option was not being honoured for Facades

This meant it was not possible to use an alias for a Facade in templates.

for example from the config (/rcrowe/twigbrige/extensions.php)
        'HTML' => ['is_safe' => true, 'callback'=> 'markup'],

I would expect to then be able to use 'markup' in the template, like so: {{ markup.whatever() }}