update: adjust intro nb

Author: VsevolodX

other/materials_designer/Introduction.ipynb

@@ -41,6 +41,10 @@
     "\n",
     "This notebook lets user add a perturbation to a slab by moving atoms according to a specified function. [Click here to open the notebook](create_perturbation.ipynb).\n",
     "\n",
+    "#### [1.8. Heterostructure creation](create_heterostructure_example.ipynb)\n",
+    "\n",
+    "This notebook lets user create a heterostructure between three materials by consequent creation of two interfaces. [Click here to open the notebook](create_heterostructure_example.ipynb).\n",
+    "\n",
     "### 2. Data Import\n",
     "\n",
     "#### [2.1. Materials import from files in ASE-supported formats](import_materials_from_files.ipynb)\n",