CONTRIBUTING.md - Update Fauna instructions to include DB & Collection setup

[MaryJoStaebler]

Is your feature request related to a problem? Please describe. While setting up the project, the Fauna portion was failing upon running. Ended up I needed to create a DB & Collections (users,streams) in Fauna.

Describe the solution you'd like Update instructions to create DB and the two current collections in the code (users, streams).

Describe alternatives you've considered Maybe have a setup inside the project to automate setting this up.

Additional context I also had to create a api key with the DB settings instead of the global one per mention in the docs.