Add ability to pass select argument to Prisma Client in adapter-prisma API

[MurzNN]

Prisma Client have ability to limit list of returning fields via select API argument. This is useful for decrease the transferred data size and increase SQL query execution.

But Keystone's adapter-prisma API at now don't provide ability to pass the select argument to Prisma Client. Will be good to add this feature.

[bladey]

Thank you for the feature suggestion @MurzNN.