Describe ignored fields in additionalProperties

[codeasashu]

Currently, the documented behaviour for ignored file is to just skip it in generated swagger schema.

However, for exactly this purpose, additionalProperties field has been added in OAS 3.0

additionalProperties will document the field as optional, which allows one to add example of optional field which may come handly for mockers and documentation.

Please add this feature

[codeasashu]

If we are to ignore dynamic keys, this is currently not possible with OAS 3

However, if we want to ignore the values of a key, we can do so.