Add README and license

[slappepolsen]

The repository presents this project as a replacement for SPSS, but it currently has no README or license file.

A README would help users understand the project’s purpose, installation, usage, and contribution process. Adding a license would clarify the permissions for reuse and distribution.

Without additional documentation (also beyond the README), users cannot reasonably evaluate whether the software is suitable for research, educational, or production use.

[slappepolsen]

In addition, and I don’t think this is just an opinion but also common sense: the contribution history credits Claude for 115 commits. AI-assisted development is not inherently a problem, but for statistical software intended for research or clinical contexts, users need sufficient information to assess reliability and accountability.