Return `true` if this headline contains a COMMENT keyword ```rust use orgize::{Org, ast::Headline}; let hdl = Org::parse("* COMMENT").first_node:: ().unwrap(); assert!(hdl.is_commented()); let hdl = Org::parse("* COMMENT hello").first_node:: ().unwrap(); assert!(hdl.is_commented()); let hdl = Org::parse("* hello").first_node:: ().unwrap(); assert!(!hdl.is_commented());
(&self)