docs: add CONTRIBUTING.md to guide new contributors

[tanmaydimriGSOC]

📌 Summary

This PR adds a CONTRIBUTING.md file, which the repository was missing.
New contributors will now understand how to set up the project, follow commit conventions, and open pull requests.

🧾 What’s Included

• New CONTRIBUTING.md file including:

  • How to clone and run the project
  • Branch naming rules
  • Commit message standards
  • PR submission instructions

🎯 Why This Is Needed

• Helps contributors onboard faster
• Standard open-source practice
• Makes the repository proposal- and GSoC-friendly

✔ Linked Issue

Fixes: <paste your issue link here>