custom filter

[arszp10]

hi

I make my geoserver using Hasura.
I use your library to generate requests with apollo-client.

I need to get a graphql request like:

query network($geom: Geometry!){
    network(where: {geom: {_st_intersects: $geom}}){
        geom
    }
}

I think that you need to do this custom filter like example

[atulmy]

@arszp10 feel free to open a PR for this use case.