feat(postman): Add Macros API collection with comprehensive examples (intercom/intercom#420117)

Add complete Postman collection for the new Macros API endpoints including:
- List all macros endpoint with basic pagination
- List macros with cursor-based pagination example
- List macros filtered by update timestamp
- Complex example combining multiple query parameters
- Get single macro by ID with error responses

Each request includes:
- Proper Bearer token authentication setup
- Required Intercom-Version header for Unstable API
- Detailed parameter descriptions and usage notes
- Example responses showcasing placeholder transformation
- Test scripts for response validation and cursor handling

The collection provides developers with executable examples to quickly
test and integrate the Macros API without writing code first.

🤖 Generated with Claude Code

Co-Authored-By: Claude <[email protected]>

Author: levindixon