Build npm Package: near-tx-decoder - Transaction Decoder

Description

## Overview
Create an npm package that decodes NEAR transactions into human-readable format - explaining what each transaction does.

## Why This Matters
Raw transactions are hard to understand. A decoder makes blockchain activity accessible to users and developers.

## Technical Requirements
- Decode all transaction action types
- Human-readable explanations
- Support for known contract ABIs
- Format for display in UIs
- TypeScript types included

## Deliverables
1. npm package: near-tx-decoder
2. Support all action types
3. Extensible ABI registry
4. Documentation