Description
Awesome! A simple way to finally convert videos to animated GIFs (or APNGs, by subtly changing a parameter or three), with few commands/arguments to remember and/or fine-tune!
While this is an amazingly clever usage of ffmpeg piped into ImageMagick, I think that you ought to update the README to explain that you need to have those two tools installed on your system. Oh, and that you need to have something installed that is able to understand sh-like shell script (not PowerShell!) — which should be the case in most Unix and Unix-like systems out there (including WSL).
Granted, for those in a Mac environment (or a Linux environment) using Homebrew, brew install gifify will immediately figure out those dependencies. But not everybody uses that; Ubuntu doesn't have it in their own package manager (just to give one example).
It's just a thought, really. The script works as intended — if you have all the requirements! — and is complete and perfect and will work "forever", or at least until either ffmpeg or convert change their list of parameters/arguments/commands... which is not very likely to happen in the next decade or two.