Add GSON support

[Ali-RS]

Hi @rvandoosselaer

It will be nice to add an API that can work with both GSON or Jackson. So those already using GSON won't need to also add Jackson.

Thanks

[rvandoosselaer]

Thanks for the suggestion. I’ll keep it in mind for the next release. I used GSON in another project and it was a breeze to use.

I defaulted to Jackson for Blocks as I already knew it and it’s straightforward for simple use cases.