Adding programming ligatures from FiraCode to my favorite Iosevka font.
Although Iosevka has ligatures, but it's not work with my kitty terminal (kovidgoyal/kitty#297). And FiraCode has some ligatures that I need.
FiraCode v4 has infinite-length that I don't want to use and has some bugs on kitty (tonsky/FiraCode#1081). So I will use FiraCode v3.1 for my font.
![NOTE] TODO: I will try to get some ligatures in higher version to my font in the future.
This script requires FontForge to build font. AFAIK, you can must python-fontforge (Debian/Ubuntu or ArchLinux) or fontforge (Gentoo, OpenSUSE).