Add rssrssrss to "Combine multiple feeds into one" sub-section

[sr093906]

https://www.rssrssrssrss.com/

A service from Buttondown, with code available at https://github.com/buttondown/rssrssrssrss

[AboutRSS]

Thanks for the recommendation ! Going to introduce it in my TG channel. You are welcome to submmit the PR so that you could be a contributor of the repo.