docs/cityhub: add ble.broadcast

A workaround has been implemented in the firmware so this is available
now.

doc/main/hubs/cityhub.rst

@@ -21,8 +21,7 @@ City Hub
 
     .. rubric:: Using connectionless Bluetooth messaging
 
-    ``ble.broadcast()`` does not work on ``CityHub`` due to a bug in the
-    Bluetooth chip firmware.
+    .. automethod:: pybricks.hubs::CityHub.ble.broadcast
 
     .. automethod:: pybricks.hubs::CityHub.ble.observe
 
@@ -85,6 +84,12 @@ Creating light animations
 Bluetooth examples
 ------------------
 
+Broadcasting data to other hubs
+*******************************
+
+.. literalinclude::
+    ../../../examples/pup/hub_common/build/ble_broadcast_cityhub.py
+
 Observing data from other hubs
 ******************************