Handle variables

Upsilon/Utilities/NodeStringFormatter.cs

@@ -16,6 +16,10 @@ namespace Upsilon.Utilities
                 sb.Append("|-- ");
             }
             sb.Append(token.Kind);
+            if (token is SyntaxToken node && node.Value != null)
+            {
+                sb.Append($" - {node.Value}");
+            }
             foreach (var syntaxNode in token.ChildNodes())
             {
                 sb.Append("\n");