Thanks for your work on this library!
I needed some features that were missing — namely, access to the libpg_query parsing for Pl/PgSQL functions, and the ability to do parsing asynchronously from Node — so I made my own fork and published it to npm as pg-plpgsql-query-native. To handle the async stuff, I also updated the C++ code to use the Node Addons API bindings to N-API.
Just thought I'd let you know in case you want to expose async parsing as part of your pg-query-parser package.