[DOCS] Update benchmark.md

[fkrause98]

📚 Documentation

The benchmark.md should be the go-to reference document on how to load test and measure the engine's performance,
but currently it's outdated, we should update it with the following guidelines:

1. First of all, ALWAYS register the specs and OS of the machines you’re using.
2. Write down every relevant command/function that you use, be it the shell or the codebase of the game.
3. Also, always write down each parameter combination you’re using.
4. Use multiple sources for load testing and benchmarks, like htop, etop, fprop, NewRelic.
5. Pictures/ Logs > Videos, maybe use videos when performance affects UX.
6. Log your results on a folder on the repo, this is important since we want to track advancements and regressions.
7. Of course, update the API of the functions accordingly.
8. This kind of benchmark is experimental, but we should always do the same
   to have a valid way to compare if we’ve advanced or regressed.