List fields have no filters in CollectionFilter

[erikgaal]

Describe the bug
List fields have no filter inputs in the CollectionFilterType.

To Reproduce
Add a list field to a definition and no filter input fields are created for it. In the following example there are no filter inputs in the ArticleFilter for the values field.

class ArticleDefinition {
    use Introspectable;

    public function fields(): array
    {
        return [
            'title' => Bakery::string(),
            'values' => Bakery::string()->list(),
        ];
    }
} 

• Laravel Version: [e.g. 5.6.23]
• Bakery Version: 2.0.0-beta.1