Feature request: return default malformed-request as a JSON response

[lavin-ds]

Hi team 👋🏽

I have been using ring-json in a few of my projects, and have been wondering if it makes sense to return the default malformed response as a JSON response, instead of text in the body. I believe it is useful since most api services expect a JSON response that they try to unmarshall and may fail when making a malformed request. But this is my opinion and may not be true about other projects in the wild.

If you agree with this, I am happy to create a pull request and make the change. I currently override it by providing my own, but was wondering if more people would find it useful.

Looking forward to hearing how you feel about it. Also, I think it's an awesome library regardless of this change 🙏🏽