Render the footnote definitions.

src/context/footnote_definition.rs

@@ -32,6 +32,7 @@ impl RenderFootnoteDefinition {
 pub(crate) struct RenderRealFootnoteDefinition {
     definition_id: String,
     reference_link: String,
+    label: String,
     contents: Vec<RenderAstNode>,
 }
 
@@ -53,6 +54,7 @@ impl RenderRealFootnoteDefinition {
         Ok(RenderRealFootnoteDefinition {
             definition_id: original.get_definition_id(),
             reference_link: format!("#{}", original.get_reference_id()),
+            label: original.get_display_label(),
             contents,
         })
     }