Undo removal of mqtt_publish() from documentation in Simon's last commit (guess it was by accident)
diff --git a/src/apps/mqtt/mqtt.c b/src/apps/mqtt/mqtt.c
index b3c2946..c49000e 100644
--- a/src/apps/mqtt/mqtt.c
+++ b/src/apps/mqtt/mqtt.c
@@ -1027,6 +1027,7 @@
 
 
 /**
+ * @ingroup mqtt
  * MQTT publish function.
  * @param client MQTT client
  * @param topic Publish topic string