FGM stands for Fighting Game Mesh because this converter was made to create a custom file format (.fgm) for
a 3D fighting game in C. It takes a .glb file then converts it as the name you decided. Hence :
./bin/app input.glb output.fgm
would be pretty much how you do it. The gJSON file is a custom of the cJSON
library that can be also found on Github.