nanobench documentation suggestion

[melg8]

When running minimal example from readme:

#define ANKERL_NANOBENCH_IMPLEMENT
#include <nanobench.h>

int main() {
    double d = 1.0;
    ankerl::nanobench::Bench().run("some double ops", [&] {
        d += 1.0 / d;
        if (d > 5.0) {
            d -= 5.0;
        }
        ankerl::nanobench::doNotOptimizeAway(d);
    });
}

You get ouput like so:

ns/op	op/s	err%	total	benchmark
7.92	126,322,335.20	2.5%	0.01	some double ops

Which has less information than were shown in documenation for same example:

ns/op	op/s	err%	ins/op	cyc/op	IPC	bra/op	miss%	total	benchmark
7.52	132,948,239.79	1.1%	6.65	24.07	0.276	1.00	8.9%	0.00	some double ops

Reproducible: https://godbolt.org/z/o7nEEP3P9

Only after reading this #99 i found out about need of usage linux + perf tool to get same extended output.

I would suggest to have "default" behavior represented in readme/docs first and only then - extended version with explanation of environment/tools needed for it to work. Cause now, at least few people got confused why "hello world" example on windows, in linux docker container (which doesnt have perf by default) and even godbolt - are all showing other output than presented in readme as if it was default output.