docs: Create CONTRIBUTING.md with setup guide

[AngusHsu]

Description

Create CONTRIBUTING.md with development setup instructions.

Parent Epic

#10 - Add CONTRIBUTING.md guide

Sections to Include

Getting Started

• Prerequisites (Node.js version, npm/yarn)
• Clone and install instructions
• Running tests locally
• Building the project

Development Workflow

• Branch naming conventions
• Commit message format
• PR process
• Code review expectations

Project Structure

• Directory layout explanation
• Key files overview
• How validators are organized

Template

```markdown

Contributing to idnumbers

Thank you for your interest in contributing!

Getting Started

Prerequisites

• Node.js 16 or higher
• npm or yarn

Setup

\`\`\`bash
git clone https://github.com/identique/idnumbers-npm.git
cd idnumbers-npm
npm install
npm test
\`\`\`

Development Workflow

...
```

Acceptance Criteria

• CONTRIBUTING.md exists in root
• Setup instructions work
• Workflow is documented

Labels

documentation, contributing, good-first-issue

[VidhyaDivakar]

Hi AngusHsu, can I work on this issue?

Thanks
Vidhya

[AngusHsu]

Hi @VidhyaDivakar,

Thank you for your interest in contributing! Yes, please go ahead and work on this issue.

The issue description already includes the sections to cover and a template to follow. A few things to keep in mind:

1. Create the CONTRIBUTING.md file in the root directory
2. Verify the setup instructions actually work by testing them yourself
3. Feel free to reference other similar projects for inspiration on structure and clarity

When you're ready, submit a PR referencing this issue (you can use "Closes #39" in the PR description).

If you have any questions while working on this, feel free to ask!

[VidhyaDivakar]

@AngusHsu thanks a lot. I will start working on this. Can the assignee be changed to Vidhya?

Thanks
-Vidhya