Feedback Add support for .shadergraph & .shadersubgraph file extension for attached files

It's very convenient to be able to attach .shader files directly to posts rather than needing to put them into .zip files for attaching them to forum posts. It would be nice to be able to do the same for .shadergraph and .shadersubgraph files for similar reasons, even though they're not directly human readable it still removes a small amount of hassle when sharing single files in posts.