Method node_at_offset

Returns node in given offset ```rust use orgize::{Org, ast::Headline}; let org = Org::parse("\n\n* foo\n* bar"); assert!(org.node_at_offset:: (0).is_none()); let hdl = org.node_at_offset:: (2).unwrap(); assert_eq!(hdl.title_raw(), "foo"); let hdl = org.node_at_offset:: (9).unwrap(); assert_eq!(hdl.title_raw(), "bar"); assert!(org.node_at_offset:: (999).is_

(
        &self,
        offset: impl Into<TextSize>,
    )