Add global_functions to Pipecat Flows docs

guides/features/pipecat-flows.mdx

@@ -413,11 +413,11 @@ async def on_first_participant_joined(transport, participant):
 
 <Note>For Static Flows, `initialize()` does not take any args.</Note>
 
-## Cross-Node State
+## Cross-Node Logic
 
-Pipecat Flows supports cross-node state through the `flow_manager.state` dictionary. This persistent storage lets you share data across nodes throughout the entire conversation.
+### State
 
-**Basic usage**
+Pipecat Flows supports cross-node state through the `flow_manager.state` dictionary. This persistent storage lets you share data across nodes throughout the entire conversation:
 
 ```python
 async def record_favorite_color_and_set_next_node(
@@ -428,11 +428,25 @@ async def record_favorite_color_and_set_next_node(
     Here "record" means print to the console, but any logic could go here;
     Write to a database, make an API call, etc.
     """
-    flow_manager.state["color"] = args["color"]
+    flow_manager.state["color"] = args["color"] # Cross-node state setting
     print(f"Your favorite color is: {args['color']}")
     return args["color"], create_end_node()
 ```
 
+### Functions
+
+Pipecat Flows supports defining functions that are available across all nodes in your flow. They're defined in the same way as node-specific functions, but are passed into the FlowManager at initialization:
+
+```python
+flow_manager = FlowManager(
+    task=task,
+    llm=llm,
+    context_aggregator=context_aggregator,
+    transport=transport,
+    global_functions=[global_function_1, global_function_2], # Cross-node functions
+)
+```
+
 ## Usage Examples:
 
 ### Dynamic Flow (Recommended)