update readme

README.md

@@ -197,8 +197,10 @@ After the detection has finished have a look at the results using Pyrocko's
 ```bash
 lassie snuffle config.yaml
 ```
-Waveform data are loaded together with station meta data and detections as
-event markers.
-Rigtht-click and select `Panels->Lassie investigate` to open a snuffling which 
-can be used to re-run the detection on the `SMAX` trace with a different 
-threshold.
+
+![example snuffling](doc/gx/snuffling_example.png "Test with synthetic events")
+
+Snuffler opens loading waveform data together with station meta data and
+detections as event markers. Load a reference catalog to compare the detections
+to and scrutinize detection performance at different detection thresholds,
+interactively.