Use JSDoc comments in `build.mjs` and related scripts to provide type hints and better intellisense. I was having a hard time knowing what fields are available in different methods, and I found this quite helpful. I'm sure other newcomers to this part of our codegen infrastructure will find it helpful as well.
First part of #3152.
This adds a crate `oxc_traverse`, but doesn't connect it up to the
transformer or anything else yet.
I think we could merge this now - as it doesn't affect any code that's
in use - and then iterate on it to add scopes before using it in
transformer. Please see
https://github.com/oxc-project/oxc/pull/3152#issuecomment-2094965406 for
the broader picture.
