Learning about topics - tutorial

[kacperbojakowski-3di]

Updated the article "Learning about topics - tutorial".

This update is part of #6827.

Description

Related to: ros2/ros2#1725

• Title changed to "Learning about topics - tutorial".
• Sections rewritten to follow the new content model and style guide.
• Replaced command-named headings with task-oriented headings.
• Reworded explanations for clarity, especially around topic introspection.
• Improved command and output presentation by separating expected terminal output into clear console blocks.
• Clarified practical behaviour in key steps.
• Moved conceptual framing into the summary and linked to related concept docs.
• Added the FAQ section.
• Tested the procedures on Ubuntu.

Did you use Generative AI?

Yes, GPT-5 for the FAQ section.

Additional Information

Documentation updates from 3di Information Solutions, agreed with Geoff and Tully.

Backport

To be backported to Lyrical after #6998 is backported.