Add support to others json libraries

[João Henrique Ferreira de Freitas]

It's possible to use another json library instead of jiffy?

Maybe the user could set it during the runtime or compile time.

Thanks.

[Paulo F. Oliveira]

jiffy is no longer being used. jsx is now the default.

[Brujo Benavides]

Another very old issue… I guess, @joaohf just moved on considering that we didn't reply in time 😞 .