feat: external schemas

# Description

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