Feature request: Add support for projection pushdown to TVF

[paynecrl97]

I'm happy to try and contribute this myself, but I'm admittedly pretty new to DuckDb.

I was wondering if this package could expose wrappers for projection pushdown to table valued functions. I think the following would be required:

• At function registration, you'd need to be able to say that the function supports projection pushdown
• The function implementation would need to receive the projection so that it can modify its output accordingly

Do you have suggestions on how this API would/should look? Or do you have any other thoughts that might impact this work?