Cleanup / Improve readme

[archae0pteryx]

The readme could be improved as some of the steps outlines are not necessary or don't reflect current flow.

• Openzepplin is already a dependency (should be a dev dependency) and doesn't need to be installed again.
• Docs about verifying a contract are a bit vague. There are several contracts. Which are we verifying? What other contracts exist? How do we test them?
• The instructions for local dev are missing steps, local requirements (node version) and other tooling specific information.
• There is no info for contribution guidelines or the expectations around review. There are some good templates for contribution that we can use and tweak for our needs
• General gussying up. Maybe add coverage badges and / or contribution counts (ice box idea)