objective-c.md

@@ -37,6 +37,7 @@ We discuss the following subtopics on separate pages:
 - \[ObjectiveC/ForeignDeclarations Foreign declarations for Objective-C\]
 - \[ObjectiveC/Messaging Sending messages\]
 - \[ObjectiveC/Classes Objective-C classes\]
+- Categories & protocols
 - \[ObjectiveC/Naming Naming conventions\] (they are not enforced, but recommended)
 - \[ObjectiveC/MemoryManagement Memory management\] 
 - `Foreign.ObjectiveC`