glTF Shader GUI / custom inspector

[atteneder]

glTFast has a bunch of custom shaders and shader graphs. There has been some effort to create a good inspector GUI, but it's far from great.

[hybridherbst]

👀 I'm a bit biased here but I can recommend ShaderGraph Markdown :) Could also think about a "deployment" mode there so that only one script or so needs to be embedded in the end but the same workflow can be used.

[atteneder]

Closing in favor of #460