Update README.md

Author: dkxce

README.md

@@ -30,7 +30,7 @@ You can export result kmz file to HTML Map and upload it to your site.
 - [POI Comment](https://github.com/dkxce/KMZRebuilder/blob/master/bin/Debug/gpiwriter_comaddcon_help.txt) (load/save from/to desc)
 - [POI Address](https://github.com/dkxce/KMZRebuilder/blob/master/bin/Debug/gpiwriter_comaddcon_help.txt) (load/save from/to desc)
 - [POI Contact](https://github.com/dkxce/KMZRebuilder/blob/master/bin/Debug/gpiwriter_comaddcon_help.txt) (load/save from/to desc)
-- [POI Alert](https://github.com/dkxce/KMZRebuilder/blob/master/bin/Debug/gpiwriter_alert_help.txt) (load/save from/to desc) with sound & trigger options
+- [POI Alert](https://github.com/dkxce/KMZRebuilder/blob/master/bin/Debug/gpiwriter_alert_help.txt) (load/save from/to desc) with sound (wav, mp3) & trigger options
 - POI Bitmap (get/set from/to kml style)
 - POI Image (get/set from/to kml style)
 - Voice Alerts (load/save from/to desc)