Add GitHub Pages API documentation (following Apis_Library pattern)

[awickert]

Summary

Add auto-generated API documentation published to https://docs.northernwidget.com/Margay_Library/, following the same Doxygen → Doxybook2 → Jekyll (Minimal Mistakes) pipeline used by Apis_Library.

Files added (template ready to commit)

The following files have been prepared locally and mirror the Apis_Library setup:

• doxygen_NW.cfg — Doxygen config (generates XML for Doxybook2)
• .doxybook/config.json — Doxybook2 config with baseUrl: /Margay_Library/
• _docs/_config.yml — Jekyll config (Minimal Mistakes theme, docs.northernwidget.com)
• _docs/Gemfile — Ruby/Jekyll dependencies
• _docs/_data/navigation.yml — Sidebar nav pointing to Margay class
• .github/workflows/docs.yml — CI workflow: builds and deploys to gh-pages branch on every push to master

What remains before going live

1. Commit and push the template files above.
2. Add Doxygen doc comments to src/Margay.h / src/Margay.cpp where missing.
3. In the GitHub repository Settings → Pages, set the source to the gh-pages branch.
4. Update the ### Reference section of Project-Margay README to point to https://docs.northernwidget.com/Margay_Library/.

Reference

• Working example: Apis_Library docs
• Workflow source: .github/workflows/docs.yml in Apis_Library