Build npm Package: @near-js/events - Contract Event Listener

Description

## Overview
Create an npm package for subscribing to and processing NEAR contract events.

## Why This Matters
Event-driven architectures need reliable event streams. This package simplifies event handling.

## Technical Requirements

### Event API
```typescript
import { EventListener } from '@near-js/events';

const listener = new EventListener({
contractId: 'token.near',
eventTypes: ['ft_transfer', 'ft_mint']
});

listener.on('ft_transfer', (event) => {
console.log(`Transfer: ${event.amount} from ${event.from}`);
});

await listener.start();
```

## Deliverables
1. **Event listener package**
2. **Real-time subscriptions**
3. **Event parsing**
4. **Reconnection handling**

## Budget: 8 NEAR

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