Another encoder (because nvtt encoder seems slow... but why?)

[funatsufumiya]

I recently created new encoder: https://github.com/funatsufumiya/GVEncoder

I really love ofxExtremeGpuVideo and GVVideo format ( I also ported to Godot and Bevy (rust) ). But long time I wondered why nvtt_encoder is slow. The another encoder above is using CPU, but much faster. I'd like to investigate reasons.

By the way, I before created utility tool with python, to check GV Video is valid. This is useful for tiny checks and maintenances. https://github.com/funatsufumiya/gv-video-header-checker