[WIP] Add CONTRIBUTING guide and issue/PR templates

[Copilot]

• Create CONTRIBUTING.md with development setup, testing, and code style instructions
• Create .github/ISSUE_TEMPLATE/bug_report.yml for structured bug reports
• Create .github/ISSUE_TEMPLATE/feature_request.yml for feature requests
• Create .github/PULL_REQUEST_TEMPLATE.md for PR submissions
• Verify all files are properly formatted and follow the repository style

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add CONTRIBUTING guide and templates</issue_title>
<issue_description>### Description
The repository lacks contribution guidelines and issue/PR templates.
This makes community contributions less structured.

Expected Behavior

Contributors should have clear instructions on:

• Development environment setup
• Code style / linting
• How to file issues or submit PRs

Suggested Fix

• Add CONTRIBUTING.md with setup, testing, and code-style instructions.
• Create .github/ISSUE_TEMPLATE/bug_report.yml and feature_request.yml.
• Add .github/PULL_REQUEST_TEMPLATE.md.
• Enable Discussions for questions and ideas.

Example

## Contributing
1. Fork the repo  
2. Create a feature branch (`git checkout -b feature/foo`)  
3. Run tests (`pytest`)  
4. Submit a PR following our template
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Add CONTRIBUTING guide and templates #83

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[henrylee97]

@hyun-hyang, Thank you for your interest in our project. However, we kindly decline AI-only contributions.