Upload sbws releases in dist.torproject.org

Some Core Tor components use https://dist.torproject.org/ to upload releases. It would be useful to have sbws releases also published there. They should be created with git archive and gpg signed. They can be created from sbws tags (that are already currently signed). This would be also facilitate sbws debian package (legacy/trac#26848 (moved)) to detect when there are new sbws releases without depending on Github automatic releases from tags.

I think this would require to create a directory called sbws, give permissions to pastly (and optionally juga).