Add an option to use https://github.com/imagemin/imagemin-gifsicle for lossless compression for GIFs, toggle in preferences:
Enable GIF compression
Lossless :radio_button:
Lossy :radio_button:
Defaults to lossless.
Actually, it's https://github.com/kornelski/giflossy
Updated the original issue description to specify the lossless option.
Just realised this is a duplicate of #117