message: Update readme to reflect classname options
diff: @@ -96,6 +96,9 @@ const embla = EmblaCarousel(node, {
  loop: false,
  speed: 10,
  startIndex: 0,
  + selectedClass: 'is-selected',
  + draggableClass: 'is-draggable',
  + draggingClass: 'is-dragging',
  })
  ```
  @@ -117,6 +120,15 @@ Carousel speed when using buttons to navigate. A higher number will make transit
  **`startIndex`** (number)
  Zero based index of the starting slide when carousel mounts.
  +**`selectedClass`** (string)
  +Classname that will be applied to the selected slide.
  +
  +**`draggableClass`** (string)
  +Classname that will be applied to the wrapper when the carousel mounts if draggable is set to true.
  +
  +**`draggingClass`** (string)
  +Classname that will be applied to the wrapper when a pointer is dragging the carousel.
  +
  ## API
  Embla exposes a set of methods upon setup that can be used to control the carousel externally. Example usage looks like this...
  