Unused deps: cfg-if, mime_guess, sysinfo

Unused dep openssl. There are mentions of it being used for "remote compilation". I have no idea what that means, or how it would work by adding a dependency like this. Not only openssl is not referenced anywhere in code, but it's not even a build/dev dependency, and there is no build.rs file.

Depends on ffmpeg-sidecar which apparently downloads ffmpeg binaries from weird places if ffmpeg is not in $PATH, a crate apparently "inspired" by webshits, and based on a GitHub action (which clearly has a very different threat model compared to executing those binaries on end-user machines).