message: docs(guide/index): embed codepen slider demo
diff: @@ -52,6 +52,14 @@ slider
  })
  ```
  +<iframe height="265" style="width: 100%;" scrolling="no" title="interact.js
  +simple slider"
  +src="https://codepen.io/taye/embed/GgpxNq/?height=265&theme-id=dark&default-tab=result"
  +frameborder="no" allowtransparency="true" allowfullscreen="true">
  + See the Pen <a href='https://codepen.io/taye/pen/GgpxNq/'>interact.js simple slider</a> by Taye A
  + (<a href='https://codepen.io/taye'>@taye</a>) on <a href='https://codepen.io'>CodePen</a>.
  +</iframe>
  +
  Installation
  ============
  