message: Updated link to styled-systems. Previous link 404'd
diff: @@ -52,6 +52,7 @@ A code coverage report is included in the `npm test` output, and test coverage d
  ## Tools we use
  1. We use [styled-components](https://www.styled-components.com/) to style our components.
  +2. We use style functions from [styled-system](https://styled-system.com/) whenever possible, and styled-systems' `style()` function to create new ones.
  ## Component patterns
  