Expose LogicalType(s) for columns in QueryResult

Hello!

I am working on the driver for (Cube)[https://github.com/cube-js/cube], and right now, there is a limitation in API, which protects us from making integration better.

We use the `stream` method that returns `QueryResult,` which implements an async iterator (return rows), but there is no way to get column types.

As I can see from DuckDB's source code, it exists in `QueryResult`, but it's not exposed in `duckdb-node`

Thanks