sort: implement GNU's orderings, keys, check mode and file handling - #200

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: engineerd/configurator@v0.0.10. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/