Adding the `'category` completion property to commands

Hi, Emacs 31 has support for the 'category completion property (I forgot if Emacs 30 also has this). Do you think you could add category metadata to the org-node commands sometime? This would include `org-node-find` and `org-node-set-tags-here` (and similar). I'm not sure what they should be yet, but you can go with what you think is best for now: there isn't an analogue to `org-node-find` upstream and `org-set-tags-command` doesn't have a category yet. With this, I'll be able to use Emacs 31's `completion-category-overrides` to match org-node's commands :)