grass.jupyter: Clarify InteractiveMap documentation (OSGeo#4243)

Clarify using different backends
Fix icons

doc/notebooks/jupyter_tutorial.ipynb

@@ -211,18 +211,19 @@
    "source": [
     "## Interactive Map Display\n",
     "\n",
-    "The `InteractiveMap` class displays *GRASS GIS* rasters and vectors with [*folium*](http://python-visualization.github.io/folium/) or [*ipyleaflet*](https://ipyleaflet.readthedocs.io/en/latest/)."
+    "The `InteractiveMap` class displays *GRASS GIS* rasters and vectors with [*folium*](http://python-visualization.github.io/folium/) or [*ipyleaflet*](https://ipyleaflet.readthedocs.io/en/latest/).\n",
+    "Backend is detected automatically; when both libraries are available, ipyleaflet is used. The backend can be also selected with the `map_backend` parameter."
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "When using ipyleaflet, the map display includes a button for querying data (ℹ️), a button for displaying and editing computational region (◻️), and a button for drawing simple vector geometries (🖉) that can be saved as a GRASS native vector map.\n",
+    "**Only when using ipyleaflet**, the map display includes a button for querying data ( ℹ ), a button for displaying and editing computational region (□), and a button for drawing simple vector geometries (🖊) that can be saved as a GRASS native vector map.\n",
     "\n",
-    "1. Query raster/vector layers: Click the **info** button (ℹ️) to enable query mode, then select a point on the map to retrieve information. Toggle the button off when finished.\n",
-    "2. Draw and save geometries: Click the **pencil** button (🖉) to draw shapes on the map, name the vector map, and save it. The geometry will be added as a new layer and the drawing tool will close automatically.\n",
-    "3. View and edit the computational region: Click the **computational region** button (◻️) to display and optionally adjust the region. Update it by clicking **Update region**, then toggle the button off when done.\n"
+    "1. Query raster/vector layers: Click the **info** button ( ℹ ) to enable query mode, then select a point on the map to retrieve information. Toggle the button off when finished.\n",
+    "2. View and edit the computational region: Click the **computational region** button (□) to display and optionally adjust the region. Update it by clicking **Update region**, then toggle the button off when done.\n",
+    "3. Draw and save geometries: Click the **pencil** button (🖊) to draw shapes on the map, name the vector map, and save it. The geometry will be added as a new layer and the drawing tool will close automatically.\n"
    ]
   },
   {