Add isUsed() to Tag model

[jeremysalmon]

Add isUsed() to check if a tag is used in database.

I use this method to check that a tag is unused and in this case delete it from the database.

For exemple when I click on the cross in livewire :

public function removeTag($tagName)
    {
        $tag = Tag::findFromString($tagName);
        $this->company->detachTag($tagName);
        $this->company->refresh();
        if(!$tag->isUsed()) {
            $tag->delete();
        }
    }

[freekmurze]

Thanks! I'm going to pass on this one, to keep the package light.

Add this in your own project.