Make RenderGraph Example

Make an example for a render graph. It is really confusing for me and a simple one file example would be great to understand it

The issue requests a simple, one-file render graph example but names no files, tests, or entry points. Start by locating the render graph implementation and existing examples, then define a minimal example that explains the basic flow. Done means the example is self-contained and makes render graphs easier to understand.

Written by the indexing model from the issue text.