Feature/add alpine container

[erseco]

This pull request introduces several improvements to the module template for Omeka S, focusing on developer experience, configuration flexibility, internationalization, and automated workflows. The most important changes are grouped below:

Dev Environment & Automation

• Added a Docker-based development stack using erseco/alpine-omeka-s:develop, with simplified configuration, auto-import of sample data, and support for module enabling via Makefile and container hooks (docker-compose.yml, Makefile). [1] [2]
• Introduced GitHub Actions workflows for CI (linting, testing, i18n checks) and automated release packaging, streamlining both development and deployment (.github/workflows/ci.yml, .github/workflows/release.yml). [1] [2]

Configuration & Settings

• Expanded the module’s configuration form to support multiple demo fields, persisting their values in Omeka settings, and set meaningful defaults for these fields (src/Module.php, config/module.config.php). [1] [2] [3]

Internationalization & Packaging

• Improved i18n extraction in the Makefile: now extracts both tagged and function-based strings, gracefully handles missing tools, and merges translation templates more robustly (Makefile).
• Added .gitattributes to ensure correct packaging by excluding dev files and directories from release archives (.gitattributes).

Documentation & Sample Data

• Updated README.md to provide clear quick-start instructions, usage of Makefile targets, and details about the Docker environment and sample users. Added a sample CSV for immediate testing (README.md, data/sample_data.csv). [1] [2]

Miscellaneous

• Updated Omeka version constraint to require Omeka S 4.x or later for compatibility (config/module.ini).