Docs: Add missing docstring to how_many_jokes tool (openai#1479)

Author: Abbas-Asad

examples/basic/stream_items.py

@@ -6,6 +6,7 @@
 
 @function_tool
 def how_many_jokes() -> int:
+    """Return a random integer of jokes to tell between 1 and 10 (inclusive)."""
     return random.randint(1, 10)