Update Creating-Your-First-ROS2-Package.rst (ros2#928)

Consistency in title formatting

source/Tutorials/Creating-Your-First-ROS2-Package.rst

@@ -294,7 +294,7 @@ To build only the ``my_package`` package next time, you can run:
  colcon build --packages-select my_package
 
 3 Source the setup file
-~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^
 
 To use your new package and executable, first open a new terminal and source your main ROS 2 installation.
 
@@ -323,7 +323,7 @@ Then, from inside the ``dev_ws`` directory, run the following command to source
 Now that your workspace has been added to your path, you will be able to use your new package’s executables.
 
 4 Use the package
-~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^
 
 To run the executable you created using the ``--node-name`` argument during package creation, enter the command:
 
@@ -373,7 +373,7 @@ Inside ``dev_ws/src/my_package``, you will see the files and folders that ``ros2
  This is where all your custom Python nodes will go in the future.
 
 6 Customize package.xml
-~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^
 
 You may have noticed in the return message after creating your package that the fields ``description`` and ``license`` contain ``TODO`` notes.
 That’s because the package description and license declaration are not automatically set, but are required if you ever want to release your package.