Colab tutorials (#367)

* Colab Button & Run added

docs/source/_rst/tutorials/tutorial5/tutorial.rst

@@ -1,6 +1,11 @@
 Tutorial: Two dimensional Darcy flow using the Fourier Neural Operator
 ======================================================================
 
+|Open In Colab|
+
+.. |Open In Colab| image:: https://colab.research.google.com/assets/colab-badge.svg
+   :target: https://colab.research.google.com/github/mathLab/PINA/blob/master/tutorials/tutorial5/tutorial.ipynb
+
 In this tutorial we are going to solve the Darcy flow problem in two
 dimensions, presented in `Fourier Neural Operator for Parametric Partial
 Differential Equation <https://openreview.net/pdf?id=c8P9NQVtmnO>`__.
@@ -9,6 +14,16 @@ First of all we import the modules needed for the tutorial. Importing
 
 .. code:: ipython3
 
+    ## routine needed to run the notebook on Google Colab
+    try:
+      import google.colab
+      IN_COLAB = True
+    except:
+      IN_COLAB = False
+    if IN_COLAB:
+      !pip install "pina-mathlab"
+      !pip install scipy
+      
     # !pip install scipy  # install scipy
     from scipy import io
     import torch