fix broken link

Author: gibbyfree

src/SUMMARY.md

@@ -44,6 +44,7 @@
     - [Code generation](attributes/codegen.md)
     - [Limits](attributes/limits.md)
     - [Type System](attributes/type_system.md)
+    - [Debugger](attributes/debugger.md)
 
 - [Statements and expressions](statements-and-expressions.md)
     - [Statements](statements.md)