Small fixes in parse tree docs.
@@ -24,7 +24,7 @@ Each node of the tree has following attributes:
[layout](./grammar_language.md#handling-whitespaces-and-comments-in-your-language) that
preceeds the given tree node. The layout consists of whitespaces/comments.
-- **symbol** - a grammar symbol this node is created for.
+- **symbol** (property) - a grammar symbol this node is created for.
Additionally, each `NodeTerm` has:
