Update ipyleaflet main example to show interactivity

Author: jasongrout

docs/source/ipyleaflet.ipynb

@@ -3,29 +3,58 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "1d3b8b34",
+   "id": "f2fda73d-1e28-41a8-bf5b-901e3f38866c",
    "metadata": {},
    "outputs": [],
    "source": [
     "import piplite\n",
-    "await piplite.install('ipyleaflet');"
+    "await piplite.install('ipyleaflet')"
    ]
   },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "48a5cc23",
+   "id": "644c9514-a50f-4e9e-b95f-f8560f1052de",
    "metadata": {},
    "outputs": [],
    "source": [
-    "from ipyleaflet import Map, basemaps, basemap_to_tiles\n",
+    "from ipyleaflet import Map, Marker\n",
+    "center = (52.204793, 360.121558)\n",
+    "map = Map(center=center, zoom=12)\n",
     "\n",
-    "m = Map(\n",
-    "    basemap=basemap_to_tiles(basemaps.OpenStreetMap.Mapnik),\n",
-    "    center=(48.204793, 350.121558),\n",
-    "    zoom=3\n",
-    "    )\n",
-    "m"
+    "# Add a draggable marker to the map\n",
+    "# Dragging the marker updates the marker.location value in Python\n",
+    "marker = Marker(location=center, draggable=True)\n",
+    "map.add_control(marker)\n",
+    "\n",
+    "display(map)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "790628ed-dfd6-4ac4-af2c-6ea91d1d16ef",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# We can also update the marker location from Python\n",
+    "marker.location = (52.2, 360.1)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "253e96c1-7673-43c8-86dc-9d5244ff10d0",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# We can run a python function when the marker location changes\n",
+    "# Here we'll adjust the center of the map to follow the marker\n",
+    "def on_location_changed(value):\n",
+    "    map.center = value.new\n",
+    "\n",
+    "# Call the on_location_changed function when marker.location changes\n",
+    "marker.observe(on_location_changed, 'location')"
    ]
   }
  ],
@@ -45,7 +74,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.12"
+   "version": "3.10.5"
   }
  },
  "nbformat": 4,