feat: external schemas

[EinfachHans]

Description

In one of the last updates the handling of external schemas was changed. For example we have in many contracts a schema like

"400":
  description: "Bad Request"
  content:
    application/problem+json:
      schema:
        $ref: './common/default-responses.yaml#/components/schemas/ValidationProblem'

In old versions this was just ignored, now it is resolved and the types are added to every type file. Can this behaviours be configured?

Possible solutions:

1. shared type file (preferred) - it would be cool when these are only created into a shared file once instead of every file
2. just toggle this behaviour on/off