Line up with serde_json API

[LPGhatguy]

It would be awesome if json5 (or maybe a crate next to json5?) could provide a core API that's a drop-in or near drop-in replacement for serde_json.

I'd love to let users experimentally opt into JSON5 configs instead of JSON in my project, but I'm not ready to commit 100%. This would make it extremely easy for crates to experiment with switching to json5 from serde_json.

I'm down to do this work if you think it's a good idea!