Set up code structure for lesser blocks.

src/parser/lesser_element.rs

@@ -19,6 +19,14 @@ pub struct TableCell<'s> {
     pub children: Vec<Object<'s>>,
 }
 
+#[derive(Debug)]
+pub struct LesserBlock<'s> {
+    pub source: &'s str,
+    pub name: &'s str,
+    pub data: Option<&'s str>,
+    pub children: Vec<Object<'s>>,
+}
+
 impl<'s> Paragraph<'s> {
     pub fn of_text(input: &'s str) -> Self {
         let mut objects = Vec::with_capacity(1);