- Rename heading to "HugeInt" for proper project naming and readability.
- Add clear description: a Python class for integers of arbitrary size, built
  as a learning challenge (not relying on Python’s built-in big-int support).
- Explicitly warn that the project is not intended for production use.
- Replace GitLab boilerplate/template content with concise, relevant
  documentation.
- Add a minimal Usage section with import, instantiation from int and string,
  printing examples, and a peek at the internal digit representation
  (dictionary indexed by place).
- Remove unrelated sections (e.g., CI/CD setup, integrations, contributing
  template, roadmap placeholders, badges, visuals, etc.) to reduce noise.

This commit focuses the README on the actual library purpose, basic usage, and
limitations, making it easier for readers to understand what the project does
and how to try it quickly.

No functional code changes; documentation only.