chore: Fixing the installation code block for diagrams support

Author: fgmacedo

README.rst

@@ -65,6 +65,8 @@ To generate diagrams from your machines, you'll also need ``pydot`` and ``Graphv
 install this library already with ``pydot`` dependency using the `extras` install option. See
 our docs for more details.
 
+.. code-block:: console
+
     $ pip install python-statemachine[diagrams]
 
 Define your state machine:

docs/installation.rst

@@ -16,6 +16,15 @@ To install Python State Machine, run this command in your terminal:
 
 This is the preferred method to install Python State Machine, as it will always install the most recent stable release.
 
+To generate diagrams from your machines, you'll also need ``pydot`` and ``Graphviz``. You can
+install this library already with ``pydot`` dependency using the `extras` install option. See
+our docs for more details.
+
+.. code-block:: console
+
+    $ pip install python-statemachine[diagrams]
+
+
 If you don't have `pip`_ installed, this `Python installation guide`_ can guide
 you through the process.