Introduce the corresponding non-render types.

src/context/document_element.rs

@@ -0,0 +1,11 @@
+use serde::Serialize;
+
+use super::RenderHeading;
+use super::RenderSection;
+
+#[derive(Debug, Serialize)]
+#[serde(untagged)]
+pub(crate) enum RenderDocumentElement {
+    Heading(RenderHeading),
+    Section(RenderSection),
+}