Create a render ast node type.

src/intermediate/footnote_reference.rs

@@ -2,7 +2,7 @@ use crate::error::CustomError;
 
 use super::registry::Registry;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub(crate) struct IFootnoteReference {
     footnote_id: usize,
     duplicate_offset: usize,