Handle review comment

Author: martinRenou

examples/simple-yjs-widget/notebooks/simple.ipynb

@@ -15,7 +15,15 @@
     "    value = Reactive[int](50)\n",
     "    min = Reactive[int](0)\n",
     "    max = Reactive[int](100)\n",
-    "    step = Reactive[int](1)"
+    "    step = Reactive[int](1)\n",
+    "\n",
+    "    @value.watch\n",
+    "    def _watch_value(self, old, new):\n",
+    "        # Watch the value of the slider, and print the new value change\n",
+    "        #\n",
+    "        # From JupyterLab, show the log console with info level to see the print\n",
+    "        # \"Ctrl + Shift + C\" then type \"Log Console\" to expand that panel\n",
+    "        print(f\"value changed: '{old}'->'{new}'\")"
    ]
   },
   {