pub fn templates(mut self, val: Vec<Template<G>>) -> Self {
        for template in val.into_iter() {
            self = self.template(template);
        }
        self
    }
Sets all the app's templates. This takes a vector of templates.

Usually, it's preferred to run `.template()` once for each template,
rather than manually constructing this more inconvenient type.
packages/perseus/src/init.rs