chore: add CONTRIBUTING and SUPPORT files

[dasanra]

What it solves

Adds CONTRIBUTING and SUPPORT files in order to guide developers how to use this repository.

Adds many more links to the docs so the reference is easier to find.

• In the CONTRIBUTING we ask devs not to open issues for usability questions and redirect them to the SUPPORT file.
• In the SUPPORT file we explain that the main source of information after the docs should be Stack Exchange and explain how to add a question there.
• In the CONTRIBUTING we explain how to use the monorepo (install dependencies, build the project...)
• Link CONTRIBUTING and SUPPORT on each package README.
• Remove API reference from protocol-kit and api-kit README