document the new shortcuts

documentation.txt

@@ -172,6 +172,10 @@ ummr -> umount maemo root"
 enftp -> enable ftp (anon upload/download everywhere)"
 mse -> enable mass-storage mode"
 msd -> disable mass-storage mode"
+usbne -> enable usb networking
+usbnd -> disable usb networking
+chargebat -> start battery charging
+
 
 Tab: Shift + Space
 ESC: Fn (Arrow) + Ctrl