message: docs: add quickstart
diff: # Optimism Monorepo (VERY WIP)
  +## Quickstart
  +
  +```
  +git clone git@github.com:ethereum-optimism/optimism.git
  +cd optimism
  +yarn
  +yarn lint
  +yarn test
  +```
  +
  ## Taming the Monorepo
  1. You solely use yarn workspaces for the Mono-Repo workflow.
  