Feature request: `json_add_raw` for jshn.sh

Sometimes, copying of a JSON file to another JSON file as a field object is needed.

I would like to have a command json_add_raw in the jshn library, which would allow to add an unquoted string as a field to a JSON file. While it would add extra ways to shoot yourself in the foot (certainly), it would also help users of the library work do more advanced JSON manipulation for config files.

An example use case is a module with a JSON configuration format and an arbitrary JSON metadata object field that the user should be able to set through uci or similar.