feat: Add data.gov.uk (CKAN) API wrapper

Implements a comprehensive Python wrapper for the UK's open data portal. The script follows the standard CKAN "drill-down" workflow:

- Fetches a list of all publishers (catalogues).
- Lists all datasets from a specific publisher.
- Retrieves all data files (resources) for a specific dataset.

Includes a full command-line interface for integration and testing, along with utility functions for discovering popular and recent datasets.

Author: rudrasheth