Context

We have content split between the Readme and the wiki. We should link out to the wiki and move the content to a single place.

Update: it turns out that the content was too complex with inline pre-formatting for the wiki, so the following approach was taken instead:

• Point to the Wiki for background and motivation
• Create a CONTRIBUTING.md file for the in-depth information on managing tests
• Add an "Available secrets" section and point to the AI Model Access

Definition of done

• Add the contributing guide with new section and clean up the Readme

Pitfalls

None