Extension registry Sphinx website

[jpmckinney]

Create extensions documentation website to:

• Render Sphinx directives on all (including community) extensions
• Build the docs of each version of each extension
• Render the information in extension.json (compatibility, etc.)

(Optionally, we can explore how to integrate GitHub issues for specific extensions to this website. However, I think this suggestion was made prior to issues being collected in ocds-extensions.)

Once this website exists, we can consider removing core extensions from the standard’s website – instead linking to this website – to avoid duplication.

[jpmckinney]

Related: https://github.com/open-contracting/standard/issues/704

[jpmckinney]

Closing as the ideas for the Extensions Explorer are better developed in the needs research and user stories documents, and a new repo will eventually be created.