closes #52 part of #8

in progress but I got some goals for the weekend.
I looked into some libraries and multiple places pointed me towards PyAV which wraps ffmpeg. So this is what I will try first.

There are a few goals I want to have:

• export a video offscreen
• user friendly CLI
• record with an on-screen GUI and have interactivity such as mouse/keyboard input. (resizing will break recordings so it most likely should just stop any ongoing recordings)
• better example

Some nice to have features:

• time independent recording (faster or slower than realtime), needs simulated uniforms.
• perhaps as a rendercanvas
• use hardware decoding (nvenc, qsv, ...) when available
• can we keep the frames on the GPU during all of this?
• be license compliant with the ffmpeg
• make it easy to add ShadertoyChannelVideo input in the future!