change(spo2): Display warning at start

preload/apps/spo2/__init__.py

@@ -144,6 +144,16 @@ class SPO2:
 
 
 if __name__ == "__main__":
+    disp = display.open()
+    disp.clear()
+    disp.print("ATTENTION:", posy=0)
+    disp.print("DEMO ONLY!", posy=20, fg=color.RED)
+    disp.print("RESULTS ARE", posy=40)
+    disp.print("WRONG!", posy=60, fg=color.RED)
+    disp.update()
+
+    time.sleep(5)
+
     sensor = SPO2()
     try:
         sensor.open()