Updates User Guide landing page

Author: spjuhel

doc/user-guide/index.rst

@@ -2,7 +2,13 @@
 User guide
 ====================
 
-Landing page of the user guide
+This user guide contains all the detailed tutorials about the different parts of CLIMADA.
+If you are a new user, we advise you to have a look at the `10 minutes CLIMADA <0_10min_climada>`_ 
+which introduces the basics briefly, or the full `Overview <1_main_climada>`_ which goes more in depth.
+
+You can then go on to more specific tutorial about `Hazard <hazard>`_, 
+`Exposures <exposures>`_ or `Impact <impact>`_ or advanced usage such as 
+`Uncertainty Quantification <unsequa>`_
 
 .. toctree::
    :maxdepth: 2