updated the README with HF infos

Author: perki

README.md

@@ -39,4 +39,24 @@ Example:
     }
   }
 }
-```
+```
+
+## 'series:\*/*' Events processing
+
+This version includes feature to use the preview of High-Frequency implementation on Pryv.
+
+This feature can be tested with: 
+
+- [A Mouse tracker to generate events](https://perki.github.io/pryv-app-web-hfdemo/generator/index.html?pryv-reg=reg.preview.pryv.tech)  
+
+
+Series events have been implemented as:
+
+- being happend to same "Stream" than standard events of the same type. Exemple: events of type "series:count/generic" on streamId "sampleStream" will be drawn on than events of type "count/generic" on the same stream.
+- By order Each event found will be processed, but only the last (with the higher event.time value will be monitored)
+- Monitoring is done by pulling on the API every `pullSerieFrequencyMs` ms 
+
+Todo: 
+
+- Eventually display differently Series event (maybe as "marks")
+- Make sure that all series events' measures previous to the last one are fetched. (not done now)