docs: Create country implementation template

[AngusHsu]

Description

Create a template/guide for adding new country validators.

Parent Epic

#10 - Add CONTRIBUTING.md guide

Template Contents

Directory Structure

```
src/countries/[code]/
├── index.ts # Main export
├── national-id.ts # National ID validator
├── tax-id.ts # Tax ID validator (if applicable)
└── README.md # Country-specific docs
```

Validator Class Template

```typescript
export class NationalId {
static readonly PATTERN = /^...$/;

static validate(id: string): boolean {
// 1. Normalize input
// 2. Check pattern
// 3. Validate checksum
// 4. Validate date (if applicable)
return true;
}

static parse(id: string): ParsedInfo | null {
// Extract and return ID components
}
}
```

Checklist for New Countries

• Research official ID format
• Create validator class
• Implement validate() method
• Implement parse() method
• Add to main dispatcher
• Add to getCountryIdFormat()
• Write tests (80%+ coverage)
• Document format

Acceptance Criteria

• Template file created
• Checklist documented
• Example implementation provided

Labels

documentation, template