Add GLSL inline shader code injection example

[asundqui]

Added an example called "GLSL Shaders" that shows how to write GLSL code inline in a SplatMesh modifier pipeline.

Has two examples: One is a direct GLSL code injection on the worldModifier to modulate color as a function of world x/y/z coordinate.

The second example injects a DynoBlock into objectModifier, and then GLSL dyno inside to show how to use other external variables as inputs, in this case a "time" uniform that is used to animate the rippling motion.

Screen.Recording.2025-06-20.at.11.31.03.AM.mov

Thoughts feedback, is this a good starting point for people to start hacking GLSL code into splats? @dmarcos does this example show a clean simple way to start writing GLSL code do you think?

[dmarcos]

Thanks so much!