Refactor author frontmatter to list

[kjaymiller]

Summary

This PR addresses issue #707 by ensuring that the author field in frontmatter is always a list if present. It also updates the templates to gracefully handle posts that do not have an author field.

Changes included:

• Refactored author frontmatter to be a list in _posts.
• Updated _layouts/post.html to iterate over the author list and look up bios from _data/authors.json.
• Updated _layouts/post.html, _layouts/blog-list.html, and _layouts/event-list.html to conditionally render the author section only if the author field exists.
• Added scripts/check_author_list.py as a pre-commit hook to enforce that author is a list and not empty if present.

Note

The check_author_list.py script is a temporary fix. The functionality to enforce list types for frontmatter fields will exist in a future version of frontmatter-check.

An issue should be created to update to the new version of frontmatter-check when it becomes available, at which point this script can be removed.

Note

The scripts/check_author_list.py script is a temporary fix. This functionality will be included in a future version of frontmatter-check.

TODO: Update to the new version of frontmatter-check once available (see linked issue).