docs(contributing): update the coding guideline

[Shin-kyoto]

Description

Updated the coding guideline.

To the reviewers:

• Please check whether there are any inappropriate guidelines included.
• In particular, verify if my thoughts on new/delete/free/raw pointers and throw are correct.
• If there are any other points that should be mentioned, please let me know. I'd like to add anything that can be easily incorporated.
• Please confirm if the structure of the text, the subtitles, and the paragraph divisions are appropriate.
• Regarding the ROS nodes guidelines in the ROS 2 Style Guide, I'm not sure where the link should point to, so I've linked it to class-design.md. If there is a better option, please let me know.
• Since I think that the coding guideline document is still incomplete, I have left the "Under Construction" note. Please let me know if it should be removed.

Pre-review checklist for the PR author

The PR author must check the checkboxes below when creating the PR.

• [x] I've confirmed the contribution guidelines.
• [x] The PR follows the pull request guidelines.

In-review checklist for the PR reviewers

The Reviewers must check the checkboxes below before approval.

• [x] The PR follows the pull request guidelines.

Post-review checklist for the PR author

The PR author must check the checkboxes below before merging.

• [ ] There are no open discussions or they are tracked via tickets.

After all checkboxes are checked, anyone who has write access can merge the PR.