Add table of contents and date

HPC_Python_Guide.md

 # A Short Guide to Python on the DTU HPC Cluster.
-Patrick M. Jensen, patmjen@dtu.dk
+Patrick M. Jensen, patmjen@dtu.dk, 25-11-2022
+
+**Contents**
+
+* [I. Preliminaries](#i-preliminaries)
+* [II. Setup Virtualenv](#ii-setup-virtualenv)
+* [III. Jupyter notebooks on ThinLinc](#iii-jupyter-notebooks-on-thinlinc)
+* [IV. Jupyter notebooks on the cluster in your own browser](#iv-jupyter-notebooks-on-the-cluster-in-your-own-browser)
 
 ## I. Preliminaries