restore advanced section in reference

docs/reference.md

@@ -22,3 +22,14 @@ control.inBackground(() => {
     
 });
 ```
+## Advanced
+  
+```namespaces
+devices.tellCameraTo(MesCameraEvent.TakePhoto);
+bluetooth.onBluetoothConnected(() => {});
+```
+  
+```package
+microbit-devices
+microbit-bluetooth
+```