Update Gemfile to use gem github-pages instead of jekyll:
The GitHub Pages Ruby gem bundles Jekyll and its dependencies in the versions used in GitHub Pages.
See https://pages.github.com/versions/
Add a Development container configuration (can be used in VSCode or GitHub Codespaces); it includes the Ruby version used in GitHub pages.
Gemfileto use gemgithub-pagesinstead ofjekyll: The GitHub Pages Ruby gem bundles Jekyll and its dependencies in the versions used in GitHub Pages. See https://pages.github.com/versions/Fixes #65