FEATURE REQUEST: allow for org-agenda-text-search-extra-files in org-ql-search

At the moment, one can choose to search the current buffer, all Org buffers, all org-agenda-files or a list of certain files. Would it be possible to make it an option too, to search all files in the list of org-agenda-text-search-extra-files? There, I have used directory-files-recursively to search my directory and its subdirectories.

If I try to search the directory by entering the path at org-ql-search, I get the error "Not an Org buffer: PATH". So org-agenda-text-search-extra-files would be a great solution.

By the way, thank you for the great org-ql package!