I found the issue now. I published a new version of the library with the fix. If you run npm install --save three-shader-graph@0.1.11 it should hopefully fix it.
The problem was that I had put three as a dependency instead of a peer dependency. This lead to having multiple instances of three. This update was recently made to three which introduced a new method on the Material class which is called when rendering. As the NodeShaderMaterial class in my library was extending from a class in a different instance of the three code, it did not have this new method which leads to the error of material.onBeforeRender not being a function.
I am very sorry that this happened. If you have any more issues with the library, you are welcome to message me directly or to create an issue on the repo’s in GitHub.