Special files via TSG

[BekaValentine]

Currently, we handle special files by running a custom-written Rust script for each file type. In most of these cases, we're simply processing the file to turn it into stack graphs in a uniform way. It would be good to see if we can do all of this via TSG instead, so that special files are things that stack graph users can also contribute code for without having to learn Rust.

[CleanCut]

The github/stack-graphs repository is no longer being maintained. As per #502, I'm closing all issues and pull requests before archiving the repository.