modify tutorials for plotter compatibility

tutorials/tutorial6/tutorial.ipynb

@@ -500,6 +500,15 @@
     "fig, ax = plt.subplots()\n",
     "plot_scatter(ax, pts_heart, 'Heart Domain')"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## What's next?\n",
+    "\n",
+    "We have made a very simple tutorial on how to build custom geometries and use domain operation to compose base geometries. Now you can play around with different geometries and build your own!  "
+   ]
   }
  ],
  "metadata": {