DOC: Improve onboarding and contribution experience for first-time contributors

[Smitaambiger]

Issue with current documentation:

While exploring Resonate as a prospective GSoC contributor, I noticed that first-time contributors may find it difficult to understand where to start without setting up the full backend.

This issue proposes improving the documentation by:

• Adding a beginner-friendly quick start section to ONBOARDING.md
• Fixing grammar and clarity issues in README.md
• Adding a first-time contributor section to CONTRIBUTING.md explaining the basic GitHub workflow

These changes aim to improve contributor onboarding and help new contributors prepare for future backend contributions.

I would like to work on this issue as my first contribution.

[github-actions]

👋 Hello @Smitaambiger!
Thank you for opening this issue. Our team will review it soon. 🚀

• If you can, please provide more details like steps to reproduce, expected vs. actual behavior, and screenshots (if applicable). 📌

We appreciate your contribution! 💡

[Smitaambiger]

Hi @M4dhav
I am a first-time open-source contributor and GSoC aspirant.

I am starting with documentation improvements to better understand the project, and I plan to move on to backend-related issues once I am familiar with the codebase.

Please let me know if it is okay for me to proceed with this issue.
Thank you!

[4555jan]

@Smitaambiger Actually, it’s not allowed to open a PR before the maintainer reviews and assigns the issue.
Also, please open the PR from the dev branch.