Add Contributing.md | NSoC'26

[DivyaJain-DataAnalyst]

🚀 Pull Request

📋 Description

• This PR adds a CONTRIBUTING.md file to the rent-mate repository under NSoC'26.
• It provides clear contribution guidelines, coding standards, and instructions to help new contributors get started.

Fixed Issue #40

🔍 Type of Change

• Bug fix 🐞
• New feature ✨
• Documentation update 📝
• Refactoring or code improvement ♻️
• Other (please describe):

🙋 Your Details

• Name: Divya Jain
• Email ID: divya_239179@saitm.ac.in

🧪 How Has This Been Tested?

• Verified that the CONTRIBUTING.md file renders properly in GitHub’s markdown viewer.
• Checked formatting for readability and clarity.

📸 Screenshots

✅ Checklist

• I have read the contributing guidelines.
• I have followed the code style and linting rules.
• I have added tests or explained why not.
• I have updated documentation (if needed).
• My changes do not introduce any known security issues or vulnerabilities.