Use console code-block in README.rst

GitHub will at least use syntax highlighting, some renderers will do
fancy things like copy without the prompt.

Author: cottsay

README.rst

@@ -3,7 +3,9 @@ template-package
 
 An extension for `colcon-core <https://github.com/colcon/colcon-core>`_ to act as a template for new extensions.
 
-When using this template, be sure to replace all instances of the word "template" in the repository::
+When using this template, be sure to replace all instances of the word "template" in the repository:
+
+.. code-block:: console
 
    $ find * -type f | xargs sed -i 's/template-package/colcon-package-name/g'
    $ find * -type f | xargs sed -i 's/template_package/colcon_package_name/g'