Clean up CONTRIBUTING.md

[natrius]

https://github.com/mansoorbarri/roadster/blob/main/CONTRIBUTING.md

There is some stuff i like and should stay there, there is some stuff thats harshly written and there is some stuff that is not in use anymore like the npm stuff.

Ultimately its your choice, but in general i find it not that bad and some stuff should probably just a bit reworded. If you can clean up with what you want, i'm happy to help if needed at all.