Fix broken anchor links and improve contribution guidelines

Hello, @thetutlage!

I noticed that there are many broken anchor links in the CONTRIBUTING.md file. I want to help correct them and also improve the contribution guidelines by adding more detailed information.

Can I help with it?

I have some doubts about where to point some anchor links, @thetutlage. Can you help me?

The first one is in the Coding style section. Where should I aim?

Can it be StandardJS?