You should be able to do this by enabling Allow users to upload regular files in the ACP, and leaving the allowed extension list empty, or just putting in the extensions you want to allow.
I hope that you do realise that allowing all file extensions is rather dangerous without extra precautions.
Leaving the allowed extensions list empty is something I would strongly advise against.
So perhaps you can change the code where it parses an RSS feed to reading the twitter feed instead. Or use an twitter to RSS service like https://twitrss.me/
If you wrote an IFTTT plugin though, that would be pretty cool 🙂
