Make output file names configurable

I think making the output file pattern somewhat configurable makes sense. I would like the generated files for example to be named like `{model}.model.ts` instead of just `{model}.ts`.

Maybe like they do it [here](https://github.com/unlight/prisma-nestjs-graphql#outputfilepattern)?

Start by locating the generator logic that determines emitted file names and compare the requested pattern with the linked prisma-nestjs-graphql example. Define how a configurable output pattern should be supplied and applied consistently; done means generated files can use names such as `{model}.model.ts` instead of `{model}.ts`.

Written by the indexing model from the issue text.