Make custom builds clearer

[kingosticks]

If we're building anything other than upstream's then should make that more obvious from the version. Can use cargo deb cli argument --deb-version to set something custom. Could use the short git hash, or the fork/branch name? Or both e.g. "kingosticks/spotify-access-token-logging@335dbddf" ? It should be more than just incrementing the Debian revision no (we don't even do that).