Make target values optional in find_doc_type

[Toniiiio]

find_doc_type requires the user to provide target values in order to specify the present document type.

Example: data("doc_json_in_code") find_doc_type(response_string = doc_json_in_code, target_values = "target_text")

Advantage of making the target values optional:

• The function can be used in other contexts (outside sivis) as well.

Disadvantage:

• Within sivis, target values will alway be present (?)!

--> If the function is required in another context, adapt to a custom function for that context.