I was looking at the stubs bundled at https://github.com/facebook/pyrefly/tree/main/crates/pyrefly_bundled/third_party, and I noticed that we have a metadata file for typeshed that records the repo url and the commit we've bundled, but we don't have anything like this for the non-typeshed stubs. It would be useful to record metadata for them so we know where they come from and how to update them.