Implement valuable::Valuable on serde_json::Value as a feature flag

[Vrajs16]

I am wondering if we can implement this trait from the valuable crate on serde_json::Value.

This would be really helpful with tracing and logging the serde_json::Value as a structured json.

I found this pr from 4 years ago in the valuable crate but never been merged and as the description says it should be included in this crate.

If this is something that could be merged, I wouldn't mind working on this.

Thanks!