Update benchmark results in the README

[FSMaxB]

The benchmark results in the README haven't been updated in ages, and some of the libraries have changed a lot since then. (Disclaimer: I'm the maintainer of cJSON).

I would really like to see the benchmark results updated. I tried to update it by myself (then I could have made a pull request), but I didn't get it to work, so I can't do that.

Could you please rerun the benchmark and update the results!