[#376] Support ESM

[feelform]

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[Copilot]

Pull Request Overview

This PR adds ESM (ECMAScript Modules) support to the pinpoint-node-agent package by updating the package.json configuration. The changes reorganize module-related fields and add type definitions for development tooling.

• Moves the type field to the top of the file for better visibility
• Adds explicit main and types fields for better package resolution
• Adds development dependencies for TypeScript types and build tooling

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