Create a render ast node type.

src/intermediate/document_element.rs

@@ -5,7 +5,7 @@ use super::IHeading;
 use super::ISection;
 use futures::future::{BoxFuture, FutureExt};
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub(crate) enum IDocumentElement {
     Heading(IHeading),
     Section(ISection),