pub fn add_new(&mut self, label: &str) -> TagId {
        let next_id = self.normal.len() + 1; // tag id starts at 1
        let tag = Tag::new(next_id, label);
        let id = tag.id;
        self.normal.push(tag);
        id
    }
Create a new tag with the provided label and layout,
and append it to the list of normal tags.
The ID will be assigned automatically and returned.
leftwm-core/src/models/tag.rs