how do I post or update an addon to the ModX website?

I have modified some snippet code and I’ve also written my own snippets that I think would be of use to the community, but I cannot figure out how to post these to the ModX repository.

First, is it possible to post an update to pre-exiting code that I, myself, did not originally wirte?

Second, are there instructions for how to post new snippets?

And finally, what can be done about multiple versions of the same snippet appearing in the repository? Is it possible to clean it up?