Tool for manipulating ro-crate file

[Alex-1919]

This is the preliminary version of the tool, which has all the basic functionalities for manipulating ro-crate metadata files with validation. Part of the MUST validations, the generator for the preview.html, a note/guides for using the tools to uphold the ro-crate standard and a more holistic readme file with the php doc are supposed to be patched later. To run the unit tests, please run the command docker-compose run test. To run the index.php code that creates the example ro-crate-metadata.json and ro-crate-preview.html in resources directory based on example dataset 102736, run the command docker-compose up -d --build and refresh the page http://localhost:8080/.

Summary by CodeRabbit

• New Features

  • Full RO‑Crate toolkit: create/load/validate/save crates, JSON read/write, flatten/unflatten utilities, in-memory JSON container, static HTML preview generator, CLI/demo scripts, and GigaDB example workflows.

• Documentation

  • Major README overhaul, new Guide, CHANGELOG, and usage/install instructions including HTML rendering and examples.

• Tests

  • Comprehensive PHPUnit suite covering entities, JSON utilities, preview generation, and validators.

• Chores

  • Composer, Docker and CI/test configs, coding-standard setup, assets, resources, and .gitignore updates.