Start the plain list module.

src/parser/token.rs

@@ -95,3 +95,14 @@ impl<'a> Source<'a> for Paragraph<'a> {
         self.source
     }
 }
+
+#[derive(Debug)]
+pub struct PlainList<'a> {
+    pub source: &'a str,
+}
+
+impl<'a> Source<'a> for PlainList<'a> {
+    fn get_source(&'a self) -> &'a str {
+        self.source
+    }
+}