This commit introduces a documentation website built with MkDocs and the Material theme.
Key changes:
- Added a `mkdocs.yml` configuration file.
- Renamed `docs/README.md` to `docs/index.md` to serve as the site's homepage.
- Created a GitHub Actions workflow (`.github/workflows/mkdocs.yml`) to automatically build and deploy the site to GitHub Pages on pushes to the `main` branch.