[doc] Add documentation on experiments

doc/usage/experiment.rst

+.. Copyright © 2023 Idiap Research Institute <contact@idiap.ch>
+..
+.. SPDX-License-Identifier: GPL-3.0-or-later
+
+.. _mednet.experiment:
+
+==============================
+ Running complete experiments
+==============================
+
+We provide an :ref:`experiment command <mednet.cli>`
+that runs training, followed by prediction and evaluation.
+After running, you will be able to find results from model fitting,
+prediction and evaluation under a single output directory.
+
+For example, to train a pasa model on the montgomery database
+evaluate its performance and output predictions and performance curves,
+run the following:
+
+.. code-block:: sh
+
+   $ mednet experiment -vv pasa montgomery
+   # check results in the "results" folder
+
+You may run the system on a GPU by using the ``--device=cuda:0`` option.
+
+
+.. include:: ../links.rst

doc/usage/index.rst

@@ -79,10 +79,11 @@ Commands
 --------
 
 .. toctree::
-   :maxdepth: 2
+  :maxdepth: 2
 
-   training
-   evaluation
+  experiment
+  training
+  evaluation
 
 
 .. include:: ../links.rst