Provide Benchmarks

I know some people frown upon benchmarks provided by the core team, but it's very hard to properly benchmark on Java, since the JVM needs proper warm-up and etc and most if not all the benchmarks on the internet comparing Jackson to GSON appears to be wrong (check the comments section, everyone of them have a valuable point about what's wrong).

The [HikariCP ](https://github.com/brettwooldridge/HikariCP) project provides it's own [benchmarks ](https://github.com/brettwooldridge/HikariCP-benchmark)and explains on it's documentation about the right way to test the library. This is very important since public articles can spread misinformation just for not knowing the proper way to use the library, to take advantage of its optimizations (let alone how to benchmark in java or use the JMH).

Providing benchmarks on the library only adds to end information, if the readers want an external opinion, they can feel free to look for outside benchmarks if they want to, so no negative downsides to this, the worst thing that can happen is raising the level of external benchmarks.

PS: This was moved from [this issue](https://github.com/FasterXML/jackson-docs/issues/11#issuecomment-352276850)