Update CONTRIBUTING.md, replace wiki links (#34035)

Summary:
This PR is a follow up for the contributing content move on the website:
* https://github.com/facebook/react-native-website/pull/3120

It replaces most of the CONTRIBUTING file content with a reference to the contributing overview page on the website, which has been based off the content of this file.

Additionally I have searched thought the code for the wiki links and replaces theme with the correct website links. There was an instance where comment was referring to an old and removed a while ago wiki page, so I just get rid of this link.

## Changelog

[Internal] [Chore] - Update CONTRIBUTING.md, replace wiki links

Pull Request resolved: https://github.com/facebook/react-native/pull/34035

Test Plan: N/A

Reviewed By: lunaleaps

Differential Revision: D37318814

Pulled By: cortinico

fbshipit-source-id: d3f5e5c5bd477c0de5c4f0f1d5de81f464b9f5b4