feat: implement contributing guide

[tryajitiono-ab]

Scope of PR:

• Implement contributing guide
• Implement foundation of AI-assisted development using create-plan and contribute skills.
• Add missing dependencies, e.g. Prettier, so that the AI agent can reformat the files changed.

Desktop screens

Mobile screens

[rayhan-ab]

just curious, will this convention be applied to this repo only or we can apply it to our other repos? because i've seen a lot of modals in AP are like {isOpen && }

[tryajitiono-ab]

I'm kinda hoping we can apply it to other repos because it seems awkward (from my perspective, anyway) if we already define open prop but we don't want to define open={isOpen}.

But I'd say it's case-by-case, if the component contains other components, I think return null is fine. But if it only contains the modal itself, I think we can just inline it with the prop.

Also, Ant Design docs seem to prefer that way, too: https://ant.design/components/modal#modal-demo-basic