Minor fixes in documentation (example_1 and example_12) (#361)

* [example_1/doc] Specify that step 1 is optional.
Two in

* [example_12/README.md] Fix wrong title in README.md

---------

Co-authored-by: Olivier Stasse <[email protected]>
(cherry picked from commit 40b92dd)

Author: olivier-stasse

example_1/doc/userdoc.rst

@@ -24,7 +24,7 @@ The *RRBot* URDF files can be found in the ``description/urdf`` folder.
 Tutorial steps
 --------------------------
 
-1. To check that *RRBot* descriptions are working properly use following launch commands
+1. (Optional) To check that *RRBot* descriptions are working properly use following launch commands
 
    .. code-block:: shell
 
@@ -50,6 +50,7 @@ Tutorial steps
 
     rviz2 --display-config `ros2 pkg prefix ros2_control_demo_example_1`/share/ros2_control_demo_example_1/rviz/rrbot.rviz
 
+    Once it is working you can stop rviz using CTRL+C as the next launch file is starting RViz.
 
 2. To start *RRBot* example open a terminal, source your ROS2-workspace and execute its launch file with
 
@@ -61,7 +62,7 @@ Tutorial steps
    In starting terminal you will see a lot of output from the hardware implementation showing its internal states.
    This is only of exemplary purposes and should be avoided as much as possible in a hardware interface implementation.
 
-   If you can see two orange and one yellow rectangle in in *RViz* everything has started properly.
+   If you can see two orange and one yellow rectangle in *RViz* everything has started properly.
    Still, to be sure, let's introspect the control system before moving *RRBot*.
 
 3. Check if the hardware interface loaded properly, by opening another terminal and executing

example_12/README.md

@@ -1,5 +1,5 @@
 # ros2_control_demo_example_12
 
-   This example demonstrates the switching between simulation and real hardware by means of the *RRBot* - or ''Revolute-Revolute Manipulator Robot''.
+   This example shows how to write a simple chainable controller, and how to integrate it properly to have a functional controller chaining.
 
 Find the documentation in [doc/userdoc.rst](doc/userdoc.rst) or on [control.ros.org](https://control.ros.org/master/doc/ros2_control_demos/example_12/doc/userdoc.html).