Show progress? about gifify

[kaikuchn]

This is a thin wrapper around ffmpeg. So if you want to have a progress indicator I'd suggest to install an ffmpeg fronted that provides one. E.g., https://github.com/sidneys/ffmpeg-progressbar-cli and then change the executable.

What @jclem could do is to introduce an environment variable that references the ffmpeg executable by default and use that to invoke ffmpeg. This then allows us to override it and use other frontends. Without that you'll have to change the script manually.