Add support for parsing tags in headlines.

src/compare/diff.rs

@@ -348,6 +348,8 @@ fn compare_heading<'s>(
         child_status.push(compare_object(source, emacs_child, rust_child)?);
     }
 
+    // TODO: Compare tags, todo-keyword, level, priority
+
     for (emacs_child, rust_child) in children.iter().skip(2).zip(rust.children.iter()) {
         match rust_child {
             DocumentElement::Heading(rust_heading) => {