[gazebo] Added quickstart screenshot.

Author: Murilo Marinho

docs/source/gazebo/images/screen_quickstart.png

@@ -35,6 +35,17 @@ After installation, :program:`Gazebo Harmonic` can be run with the following com
 
     gz sim
 
+Which should result in something similar to the following, if the installation went well.
+I would recommend strongly against letting the curiosity get the best of you and clicking on the ``3d_shapes.sdf`` given that it's current freezing my virtual machines.
+Other
+
+.. image:: images/screen_quickstart.png
+    :width: 100%
+
+Basic functionality of :program:`Gazebo`
+----------------------------------------
+
+We can start by choosing the file :file:`ackermann_steering.sdf`
 
 .. _curl: https://curl.se/
 .. _`lsb-release`: https://packages.debian.org/sid/lsb-release

docs/source/gazebo/installation.rst

@@ -120,21 +120,32 @@ It is important to know of the existence of ``service introspection``. Although
 After proper configuration of the server and client, :program:`ros2 service echo` allows us to look at what information is being exchanged between participants. It helps not having to
 add endless ``print`` functions throughout the code that hurt performance.
 
+We'll be working in these files
+
+.. code-block:: console
+
+    python_package_that_uses_the_services
+    `-- python_package_that_uses_the_services
+        |-- add_points_service_client_introspection_node.py
+        `-- add_points_service_server_introspection_node.py
+
 
 .. tab-set::
 
-    .. tab-item:: add_points_service_client_introspection_node.py
+    .. tab-item:: Introspection Client
 
-        :download:`add_points_service_client_introspection_node.py <../../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_client_introspection_node.py>`
+        :download:`add_points_service_client_introspection_node.py <../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_client_introspection_node.py>`
 
-        .. literalinclude:: ../../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_client_introspection_node.py
+        .. literalinclude:: ../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_client_introspection_node.py
            :language: python
            :linenos:
+           :lines: 24-
 
-    .. tab-item:: add_points_service_server_introspection_node.py
+    .. tab-item:: Introspection Server
 
-        :download:`add_points_service_server_introspection_node.py <../../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_server_introspection_node.py>`
+        :download:`add_points_service_server_introspection_node.py <../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_server_introspection_node.py>`
 
-        .. literalinclude:: ../../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_server_introspection_node.py
+        .. literalinclude:: ../../ros2_tutorial_workspace/src/python_package_that_uses_the_services/python_package_that_uses_the_services/add_points_service_server_introspection_node.py
            :language: python
            :linenos:
+           :lines: 24-