Update LivePreview.ino

Author: jacobhylen

libraries/Arduino_LED_Matrix/examples/LivePreview/LivePreview.ino

@@ -2,6 +2,8 @@
   This sketch allows live editing of the matrix pixels using WebSerial
   To test, head to https://ledmatrix-editor.arduino.cc
 
+  The LED Matrix editor is part of Arduino Labs (https://labs.arduino.cc/), and is therefore considered experimental software.
+
   Don't forget to close any serial monitor already opened.
 */