message: Added link to slackin on readme
diff: @@ -3,6 +3,8 @@ Cardstack Application Framework
  This is the main repo for [Cardstack](https://www.cardstack.com/), an open source application architecture for building cohesive experiences on open, decentralized infrastructure.
  +Join the discussion around developing on the Cardstack framework on Slack at [https://join.cardstack.com](https://join.cardstack.com).
  +
  ## Orientation
  This is a monorepo. Each directory under `packages` is distributed as a standalone NPM package under the `@cardstack` NPM namespace. Each package is a Cardstack plugin. A family of Cardstack plugins comes together to provide both browser-side and server-side functionality of a Cardstack application.
  