Added a comprehensive CONTRIBUTING.md to improve contributor onboarding

[indresh404]

Summary

Added a comprehensive CONTRIBUTING.md to improve contributor onboarding and standardize the contribution workflow for the project.

This PR also updates setup documentation to consistently use pnpm across all developer guides.

Closes #1029

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Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup

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Changes Made

• Added a structured CONTRIBUTING.md
• Added Quick Start section (<10 steps)
• Documented:
  • Prerequisites
  • Local setup
  • Environment variables
  • Code style & linting
  • Branch naming conventions
  • Conventional commits
  • PR checklist
  • GSSoC issue labels
  • Self-hosting references
• Added Code of Conduct reference
• Updated README.md setup commands to use pnpm
• Updated DEVELOPMENT.md to align with pnpm

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How to Test

1. Open CONTRIBUTING.md
2. Verify all required sections are present
3. Follow Quick Start instructions
4. Confirm all commands use pnpm
5. Verify references in:
   • README.md
   • DEVELOPMENT.md

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Screenshots (if UI change)

N/A — Documentation-only changes

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Checklist

• Linked issue in summary
• pnpm lint passes locally
• No TypeScript errors (pnpm type-check)
• Self-reviewed the diff
• Added/updated tests if applicable

[vercel]

@indresh404 is attempting to deploy a commit to the PRIYANSHU DOSHI's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[indresh404]

Hi @Priyanshu-byte-coder , along with the CONTRIBUTING/documentation improvements, I also updated pnpm-workspace.yaml in PR #1261 to fix the ERR_PNPM_IGNORED_BUILDS issue occurring with newer pnpm versions.

The update adds the required build dependency allowlist configuration for:

• core-js
• esbuild
• unrs-resolver

This ensures pnpm install works correctly across pnpm v9 and v10+ environments.