Add support for RSS

Email is great, and all, but python has an (admittedly limited) `http.server` module that should suffice to serve up basically the same content as the generated emails, but in RSS format. Something like this would probably be best suited for a container, however and your feed aggregator pointing to `locahost:XXXX`.

I'm not sure if it simplifies _anything_, I just prefer RSS over email. :smile: And I especially don't like gmail. Of course, if errata.almalinux.org supported RSS/ATOM... :100: