Support json filtering for nested fields

[jasonkuhrt]

• https://github.com/graphql-nexus/nexus/issues/947#issuecomment-675367427
• https://www.prisma.io/docs/reference/tools-and-interfaces/prisma-client/working-with-json#filtering

[RyudoSynbios]

Hi, do you know if this will fixes also #797?

[jasonkuhrt]

@RyudoSynbios don't think so