Implement source.filter from the MapBox styleJSON spec #2700
Description
New Feature
Add filtering at the source level without having to set the data attribute. This already exists as source.filter in the MapBox style spec.
Why
I would love to be able to filter sources without having to set the data attribute, and be able to filter before clustering (which layer-level filtering doesn't allow). mapbox-gl already implements this and it's super convenient.
Thank you :)