Add a test proving that nested lists are exited by two blank lines.

src/parser/plain_list.rs

@@ -267,7 +267,6 @@ mod tests {
 
     #[test]
     fn two_blank_lines_ends_list() {
-        // Plain lists with an asterisk bullet must be indented or else they would be a headline
         let input = r#"1. foo
 2. bar
    baz
@@ -291,6 +290,31 @@ mod tests {
 3. lorem
 
 
+"#
+        );
+    }
+
+    #[test]
+    fn two_blank_lines_ends_nested_list() {
+        // Plain lists with an asterisk bullet must be indented or else they would be a headline
+        let input = r#"1. foo
+   1. bar
+
+
+baz"#;
+        let initial_context: ContextTree<'_, '_> = ContextTree::new();
+        let document_context =
+            initial_context.with_additional_node(ContextElement::DocumentRoot(input));
+        let plain_list_matcher = parser_with_context!(plain_list)(&document_context);
+        let (remaining, result) =
+            plain_list_matcher(input).expect("Should parse the plain list successfully.");
+        assert_eq!(remaining, "baz");
+        assert_eq!(
+            result.get_source(),
+            r#"1. foo
+   1. bar
+
+
 "#
         );
     }