updates the widget demo notebook following pypowsybl-jupyter v1.0.0 release (#29)

Signed-off-by: Christian Biasuzzi <christian.biasuzzi@soft.it>

Author: CBiasuzzi

pypowsybl_jupyter_widgets_demo.ipynb

@@ -65,7 +65,7 @@
    "id": "3dc5dc34-2c28-411f-b281-c3cc2fd53ad4",
    "metadata": {},
    "source": [
-    "Create a network."
+    "Load IEEE 14 buses network"
    ]
   },
   {
@@ -90,9 +90,10 @@
    },
    "source": [
     "Display the network explorer widget. \n",
-    "* Click on a voltage level from the list to display its NAD and SLD in the two \"Network Area\" and \"Single Line\" tabs. \n",
+    "* Click on a voltage level from the list to display its NAD and SLD in the two \"Network Area\" and \"Single Line\" tabs. The history box, in the bottom left corner, lists the last displayed voltage levels.\n",
     "* Both diagrams can be panned and zoomed.\n",
     "* The NAD is centered on the currently selected voltage level. A 'depth' slider controls the size of the sub-network.\n",
+    "* Nodes in the NAD diagram can be repositioned using drag-and-drop. However, the new positions are not persisted: switching to a new VL and then switching back to the current VL, the original nodes layout would be restored. A SHIFT+CLICK on a node will activate the SLD tab on the corresponding voltage level. Please note that these interactions in the NAD are available only when using PyPowSyBl >= v1.8.1.\n",
     "* A third tab, \"Network map\" displays the network’s substations and lines on a map. The map is empty if the network does not contain any geographical data."
    ]
   },
@@ -130,6 +131,14 @@
     "network_explorer(n, vl_id='VL14', depth=4)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "8fcc0656-5864-46c9-8e36-75995ee60f3c",
+   "metadata": {},
+   "source": [
+    "Please note that it could take some time to compute the NAD layout, depending on the network and the depth parameter. A progress bar will indicate the computation in progress."
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "ba94b49a-979e-4c70-b66b-5c973556616d",