Exclude Bundler directories from Jekyll source during CI build

[Copilot]

Please note that if you are trying to update your website, this is the wrong place to do so. Please carefully follow the Beautiful Jekyll instructions (found at https://github.com/daattali/beautiful-jekyll#readme) and make sure you submit changes to your version of the project.

If your intention is to submit a Pull Request, this update addresses the failing Build Jekyll job by preventing Jekyll from traversing Bundler-installed gem files under vendor/, which were being parsed as posts and causing build failure.

Thank you!

• Root cause

  • Jekyll build included Bundler artifacts (vendor/bundle/...) and attempted to parse gem template post files with invalid front matter dates.

• Change

  • Updated _config.yml exclude list to ignore Bundler output directories.

exclude:
  - .bundle/
  - vendor/

• Effect

  • CI Jekyll build now only processes repository content, avoiding false post parsing from dependency directories.