Contributing guide file is outdated

[Relequestual]

The contributing guide file located at
https://github.com/json-schema-org/json-schema-spec/blob/main/CONTRIBUTING.md is out of date, and not accurate for how we are proceeding.

We should do one of the following

• Add a note to the top which states this fact
• Remove the content that is outdated
• Start the file from scratch based on our current understanding

This file will require review again once we publish the next version of the specification.

[benjagm]

I just opened a PR with a new version of the contributing guidelines of the Spec and I'd love to get feedback and reviews.