Add basic templates for plain list.

src/intermediate/plain_list_item.rs

@@ -0,0 +1,15 @@
+use crate::error::CustomError;
+
+use super::registry::Registry;
+
+#[derive(Debug)]
+pub(crate) struct IPlainListItem {}
+
+impl IPlainListItem {
+    pub(crate) async fn new<'parse>(
+        registry: &mut Registry<'parse>,
+        plain_list_item: &organic::types::PlainListItem<'parse>,
+    ) -> Result<IPlainListItem, CustomError> {
+        Ok(IPlainListItem {})
+    }
+}