Added ROS 2 Integration Tutorials

[quarkytale]

🎉 New feature

Summary

Changes:

• Added a Guide to ros_gz_project_template for ROS 2 and Gazebo Development which aims to explain how to use the template as well what comprises it and why
• Added ROS 2 and Gazebo Integration Tutorial using rrbot

Test it

Checklist

• [ ] Signed all commits for DCO
• [ ] Added tests
• [ ] Added example and/or tutorial
• [ ] Updated documentation (as needed)
• [ ] Updated migration guide (as needed)
• [ ] Consider updating Python bindings (if the library has them)
• [ ] codecheck passed (See contributing)
• [ ] All tests passed (See test coverage)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[mabelzhang]

Summarizing what we said offline for visibility: I'm fine with what's here. It can be merged after the comments are addressed and any longer remaining ones moved to an issue ticket to track them.

[quarkytale]

Created issue https://github.com/gazebosim/docs/issues/382 for tracking pending enhancements.