Colab tutorials (#367)

* Colab Button & Run added

tutorials/tutorial13/tutorial.py

@@ -2,6 +2,9 @@
 # coding: utf-8
 
 # # Tutorial: Multiscale PDE learning with Fourier Feature Network
+# 
+# [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/mathLab/PINA/blob/master/tutorials/tutorial13/tutorial.ipynb)
+# 
 # This tutorial presents how to solve with Physics-Informed Neural Networks (PINNs)
 # a PDE characterized by multiscale behaviour, as
 # presented in [*On the eigenvector bias of Fourier feature networks: From regression to solving
@@ -13,6 +16,15 @@
 # In[1]:
 
 
+## routine needed to run the notebook on Google Colab
+try:
+  import google.colab
+  IN_COLAB = True
+except:
+  IN_COLAB = False
+if IN_COLAB:
+  get_ipython().system('pip install "pina-mathlab"')
+
 import torch
 
 from pina import Condition, Plotter, Trainer, Plotter