Add example of C++ logging implementation

[cadmus-to]

(Referenced in #2026)

I'm not sure if this should be a separate issue, but it is within the scope of this one.

Under Logging Usage for C++ at the Concept page (https://docs.ros.org/en/rolling/Concepts/About-Logging.html), there probably should be a C++ implementation demo similar to the Python's one. Probably something like:

• https://github.com/ros2/demos/tree/master/logging_demo ?

Yeah just thought it'd be good to put a link for that there, in a similar fashion to the Python demo.

[kurshakuz]

Having similar content present under different languages makes a lot of sense to me. However, the package you mentioned seems to serve a little bit different purpose and is not as intuitive as Python example. I have found similar implementation in C++ which implements the same example and could fit better.

Now the only thing missing is an extensive test example for rclcpp logging.

[clalancette]

We've significantly redone the logging documentation since this issue was opened, and I now think that http://docs.ros.org/en/rolling/Concepts/About-Logging.html does a much better job of explaining what is available.

Based on that, I'm going to close this out. But feel free to reopen if you still think this is an issue.