ISF support

[Baku 麦]

FYI, Interactive Shader Format might suit for this kind of plugin.

In short, ISF is almost just a raw fragment shader file except for some custom function and metadata which is described at a beginning of the file as JSON format.

The pros is that it's much simpler to describe uniforms inside the file, and there's no need for us to prepare some UI to link between some parameters on AE and shader file.